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Sebastian

Penetraitt Serum

Finisher / Serum, lightweight

  • Finisher
  • serum
  • Sulfate-free
  • Protein-free
  • Curly-method
  • Not cruelty-free · PETA-listed
Size3.4 fl oz
Price$46seen at one store · 3.4 oz
Price / oz$13.53/ozat 3.4 oz
Where to buy2 stores · 2 sizes

Add it to your products. We’ll tell you if it’s ever recalled.

Scent:

The ingredient list declares fragrance. What it smells of is not stated, and we do not guess.

Personal fit

Is this right for you?

Complete the consultation to see how well this product fits your hair and your goals. With 6,000+ products in our library, we can match you to the right ones.

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  • Your goals, scalp, damage history, water, budget, and scent preferences all shape your plan.

$49 with 60 days of follow-up questions and plan updates

$99 with 12 months. Pay once; the year renews only if you choose.

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Upper-mid price for a serum

$13.53/oz at 3.4 oz, more than 67% of the 136 serums , which mostly run $3.94–14.80/oz. The cost less.

Price and stores

Great for

Protein-sensitive hairthat stiffens when protein is added
Fine hairthat flattens under most products
Aerosol avoidancea pump or tube, not a pressurised can

Maybe skip if

this product has a scent
Very dry or damaged hairit contains fast-drying alcohol
Anyone who dislikes a castthe film formers here can set firm
Hair that looks dullno recognised shine system in the list
Silicone-free routinesit does contain silicones, the water-soluble kind
Vegan and cruelty-freeour record does not support both claims here

Whether a finisher this rich looks shiny or greasy on you depends on your strand thickness and how oily your hair gets. Your consultation answers that.

What the formula actually does

Read from the label, not the marketing

Each row says where it comes from: F means we derived it from this product’s own ingredient list, S means it is a claim the brand makes that the formula neither confirms nor contradicts.

Weight on the hair Light

Water-first and light: unlikely to flatten fine hair.

Oils and butters None

No oils or butters in the list.

Needs detergent to remove Rinses with water

The silicones here are the water-soluble kind.

Fast-drying alcohol High in the list

Fast-drying alcohol in the first three ingredients.

Fragrance Prominent

Fragrance is in the first eight ingredients, so it makes up a larger share of the formula.

from the formula stated by the brand reported by reviewers Scale: 1 dot low · 5 dots high, within this product type.

Ingredients that matter

The ingredients that change a decision

The workhorse ingredients, plus anything lower down that changes a decision. The chips name what an ingredient does. They are not safety scores, and no ingredient here is rated good or bad on its own.

IngredientWhat it doesWhy it mattersChip
Alcohol Denat. drying alcohol Speeds drying but can leave hair feeling dry Drying
Water solvent The base everything else is dissolved in Neutral
Niacinamide vitamin A marketed vitamin addition Detangles
Peg/Ppg-20/23 Dimethicone emulsifier Keeps oil and water mixed Shine
Caffeine active The over-the-counter active Active
FragranceParfum fragrance The scent Fragrance
Acrylates/C10-30 Alkyl Acrylate Crosspolymer thickener Adjusts the texture Holds
Sodium Hyaluronate humectant Adds a little water-binding Moisturizes
Hexyl Cinnamal fragrance The scent Fragrance
Benzyl Salicylate fragrance The scent Fragrance
Linalool fragrance The scent Fragrance
Citronellol fragrance The scent Fragrance
What the list leaves out, and what it carriesThe list carries no sulfates. No protein: a moisture formula, not a repair one. Fragrance is on the label. Contains fast-drying alcohol.
Full ingredient list (16)

In the US, ingredients above 1% are listed from most to least. Below 1% they can appear in any order. Each note keeps three things apart: what the ingredient generally does, its role in this type of product, and what its position can tell you.

  • 1 Alcohol Denat.
    General function

    Fast-drying alcohol used to make sprays set quickly. In leave-on products it can leave hair feeling dry, especially in high position on the list.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitFine or easily flattened hair

    Evaporates on contact, which is how a spray sets almost instantly and leaves no weight behind it.

    May not suitDry, coarse, or high-porosity hair

    Porous hair gives water up easily as it is; a fast-evaporating solvent high on the list accelerates that.

    May not suitVery dry or highly damaged hair

    It evaporates quickly and takes some water with it. On hair already short of moisture, a formula built on a lot of it can finish drier than it started.

    PubChem
    • drying alcohol
    • solvent
  • 2 Water
    General function

    The base of almost every rinse-off and cream hair product. It carries everything else and is normally the first ingredient on the label.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    • solvent
  • 3 Niacinamide
    General function

    Vitamin B3, used in scalp products for conditioning claims.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitFrizz-prone, damaged, or high-friction hair

    Deposits a lubricating layer that makes combing easier, which is most of what stops mechanical damage adding to frizz.

    PubChem
    • vitamin
    • conditioning agent
  • 4 Peg/Ppg-20/23 Dimethicone
    General function

    An ethoxylated or propoxylated formulation aid. Ingredients of this family keep oils, silicones and fragrance evenly dispersed in a water-based product.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    • emulsifier
    • silicone
    • water-soluble silicone
  • 5 Caffeine
    General function

    Included in scalp and thickening products for label appeal. Evidence for applied caffeine changing hair growth is limited.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    PubChem
    • active
  • ▾Below about here, the order stops meaning much. These are usually used at 1% or less.
  • 6 Fragrance · Parfum
    General function

    An undisclosed blend of scent ingredients. Regulations let it stay unlisted, so a fragrance-free product is the only way to be certain what is not in it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    Declared fragrance. On a fragrance-sensitive routine this is the line that decides it, wherever it sits on the label.

    • fragrance
    • declared fragrance
  • 7 Acrylates/C10-30 Alkyl Acrylate Crosspolymer
    General function

    A gel-forming thickener that also keeps oils suspended. It contributes a little hold.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitClimate-sensitive or frizz-prone hair

    A set polymer film is a physical barrier to humidity, so a style keeps its shape longer in damp conditions.

    May suitMaximum-hold styling

    Synthetic film formers dry into a continuous film, which is what holds a shape against movement and against humid air.

    DependsBuild-up-sensitive routines

    Some acrylate copolymers rinse with water and some need a detergent; the label alone does not say which one a formula used.

    • thickener
    • polymer
    • film former
  • 8 Sodium Hyaluronate
    General function

    A large water-binding molecule that sits on the surface holding moisture.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitDry, coarse, or high-porosity hair

    High-porosity hair loses water fast; a humectant holds some of it in place for longer than the wash itself would.

    May suitVery dry or highly damaged hair

    Binds water into the outer layers of the strand, and water is what makes dry hair flexible again rather than brittle.

    DependsClimate-sensitive or frizz-prone hair

    A humectant moves water in whichever direction the air allows: it holds moisture in humid conditions and can pull it back out of hair in very dry ones.

    • humectant
  • 9 Glycerin
    General function

    Glycerin, also called glycerol, attracts moisture and mixes completely with water.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May suitDry, coarse, or high-porosity hair

    High-porosity hair loses water fast; a humectant holds some of it in place for longer than the wash itself would.

    May suitVery dry or highly damaged hair

    Binds water into the outer layers of the strand, and water is what makes dry hair flexible again rather than brittle.

    DependsClimate-sensitive or frizz-prone hair

    Water moves both ways. Measured across concentrations, glycerin solutions give water up in some conditions and take it from the air in others. What it does for you depends on how much of it is there and on the air around it.

    Scientific Reports
    • humectant
  • 10 Hexyl Cinnamal
    General function

    A jasmine-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 11 Benzyl Salicylate
    General function

    A soft floral fragrance component listed separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 12 Linalool
    General function

    A floral fragrance component listed separately as a recognised contact allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 13 Trideceth-6
    • emulsifier
    • solubilizer
  • 14 Citronellol
    General function

    A rose-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 15 Geraniol
    General function

    A rose-scented fragrance component, listed on its own because some people react to it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    • fragrance
    • named fragrance allergen
  • 16 Limonene
    General function

    A citrus-smelling fragrance component that EU rules require to be named separately because some people react to it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen

What the whole list adds up to

  • 7 fragrances
  • 6 named fragrance allergens
  • 2 solvents
  • 2 emulsifiers
  • 2 humectants
  • 1 drying alcohol
  • 1 vitamin
  • 1 conditioning agent
  • 1 silicone
  • 1 water-soluble silicone
  • 1 active
  • 1 declared fragrance
  • 1 thickener
  • 1 polymer

Ingredient list captured 2026-08-27. Formulas change, so check the package in your hand when an ingredient matters to you.

Price · 3.4 oz

Seen at $46 1 store · checked Aug 28
Good value under $10 Under $3.04/oz it costs less than three-quarters of the 7 products we score as doing the same job

Priced above the products that do the same job. Stores sell it above the $10 line; products that do this job typically go for about $18 at this size.

Sizes

3.2 oz
$30.69
$9.59/oz
3.4 ozusual store size
$46
$13.53/oz

The 3.2 oz costs the least per ounce, 29% less than the 3.4 oz.

Show the price ladder
Where we’ve seen it2 listings · 2 stores

3.4 ozusual store size

  • Ulta
    $46.00
    3.4 oz · $13.53/oz
    Aug 28Lowest per oz

3.2 ozBest per ounce

  • ShopSimon
    $30.69
    3.2 oz · $9.59/oz
    Sep 5Lowest per ozSale · was $42.00

Sorted by price per ounce. Dated observations from our research, not live prices. Direct store pages, no affiliate links. We don’t sell this product.

How we work this out
  1. 3.4 oz is the size stores list most often; every comparison on this page is made at it. Other sizes are shown in the Sizes row and the store list.
  2. Seen at $46 is the price we have observed for the 3.4 oz. We need three stores before we call a price commonly seen.
  3. Good value under $10 comes from the 7 products we score as doing the same job as this one. A quarter of them cost less than $3.04/oz; at 3.4 oz that is $10. Under that line you are paying less than most of them.
  4. Each size is guarded on its own, so a multipack or a marketplace listing at one size cannot move another.
  5. About $18 is what those same products typically cost at this size: the midpoint of their prices per ounce, scaled to 3.4 oz.

Formula

Formula score
6 of 10

Nothing separates this from the middle of the range for serums, on formula or on cost per ounce.

How the score is counted
  • 2 products that do the same job cost less per ounce
  • Costs more per ounce than 67% of the 136 serums we’ve priced
  • No oils or butters in the working zone in the formula
  • Prestige tier, sold at Ulta and Salons
  • A shine systemThe silicone, oil, or ester that produces gloss.3 pts
  • A weightless carrierDelivers the shine without leaving grease.2 pts
  • Oils or butters in the working zoneSoftens the strand rather than just coating it.2 pts
  • An antioxidantKeeps the oils in the bottle from going off.1 pt
  • No drying alcohol in the first threeFast drying without leading on alcohol.1 pt
  • Fragrance kept out of the top eightScent as a finishing touch, not a major share.1 pt

The formula score measures completeness for the job: a weighted share of the systems this product type is usually built around that we find in this list. It does not rate how well the product works or its quality, and it never compares across product types.

Does the same job, for less

Formulas that do the same things (cleanse, condition, coat or hold) for less per ounce. Scent, texture and where you buy them can still differ.

DavinesClosest function This is a Dry Wax Finishing Spray $6.07/oz $7.46/oz less
  • Protein-free
  • Lightweight
Function
  • Water-binding (humectants)
  • Propellant
Also
  • Cruelty-free
  • Salon tier
Compare
Garnier FructisLowest cost per oz Style Sleek & Shine Flat Iron Perfector Flexible Hold Straightening Mist $0.87/oz $12.66/oz less
  • Heat protect
  • Protein-free
  • Lightweight
· Close function
Function
  • Film formers
  • Oils and butters
Also
  • Drugstore tier
Compare

See more alternatives in the product library

These products do a similar job. We haven’t matched them to you. Find the one that fits your hair, routine and budget

Suits every hair pattern

Final decision

Should you buy it?

Only for a specific need
Best user

Hair that stiffens on protein, for a protein-free formula and something that will not weigh hair down

Biggest tradeoff

Worth skipping for anyone sensitive to fragrance, very dry or high-damage hair, or anyone who will not scrunch out a cast

We do not sell products or take placement fees. This page states what the formula and the prices show; the consultation is what matches it to a person.

More from Sebastian

How this page was made

  • Everything above comes from our researched product record: identity, the ingredient list as printed, the brand's own claims, dated prices and review themes our researchers wrote in their own words. No part of this page is written by hand for one product.
  • The value band is a fixed label over two stored numbers: this product’s cost per ounce as a percentile of every product of this type we have priced, each at the size it is most often sold in, and how many products we score as doing the same job cost at least a quarter less per ounce.
  • Both scores out of ten are defined on this page. The formula score is completeness for the job, computed from a fixed per-format checklist shown beneath the gauge; the price score is cost per ounce against every product of this type we have priced.
  • The "Is this right for you?" panel reads only your own consultation answers, and it applies exactly the filters our recommendation engine applies. It is computed when you load the page and is never stored on it.
  • 2 sources consulted for this product (0 manufacturer or regulatory, 1 retailer, 1 editorial), last checked 2026-09-05.
  • Ingredient references are linked for 8 of 12 product-aware annotations on this page. Fit notes are general formulation guidance. They aren’t a verdict on the finished product or on you.
  • We haven’t tested this product in a lab, and we don’t physically test your hair. Formula readings come from the ingredient list. Claims about how it behaves are labelled as the brand's.
  • Ingredient order tells you relative amount only above roughly 1%. Prices are what we saw on the dates shown and can change.
  • Ingredient names link to our ingredient library, where each entry shows what it does, which product types use it, and where it usually sits on a label across everything we have researched.
  • This is cosmetic information, not medical advice, and nothing here diagnoses or treats a health condition.
  • Formula readings: derivation v23. Record last updated 2026-09-09.

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