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Side by side

K18 Pro Molecular Repair Hair Mask vs Paul Mitchell Bond Rx Step 1 Professional Bond Builder

93% function match · 6 of the 7 functions we compared match Formula overlap 51%. K18 Pro Molecular Repair Hair Mask and Paul Mitchell Bond Rx Step 1 Professional Bond Builder share 2 ingredients among each other's most prominent.

Based on your consultation

Which of these fits your hair?

We check your pattern, moisture need, scalp, fragrance tolerance, weight sensitivity and more against each formula — and say which one lines up.

Your profile at a glance

  • Your answers appear here
  • Your answers appear here
  • Your answers appear here
  • Your answers appear here

When each one is the right call

What each formula is built for, from its own ingredient list.

  • Pro Molecular Repair Hair Mask — protein-hungry hair
  • Bond Rx Step 1 Professional Bond Builder — protein-hungry hair

Side by side

Every trait, aligned

One row per trait, read from each product’s own ingredient list and record. A dash means we have not researched that field for that product — it is not a “no”.

Trait
K18

Pro Molecular Repair Hair Mask

  • Mask / treatment
  • Prestige
  • Sulfate-free
  • Silicone-free
Paul Mitchell Bond Rx Step 1 Professional Bond Builder — 8.5 oz container Paul Mitchell

Bond Rx Step 1 Professional Bond Builder

  • Mask / treatment
  • Prestige
  • Moisture-rich
Price, size & price per ounce
$69.16 5 oz · $13.83/oz
$65 8.5 oz · $8.29/oz
Value / price positioning
Same job for less elsewhere $$$$$ Prestige tier · costs more than 98% of the 347 masks and treatments we’ve priced
Same job for less elsewhere $$$$$ Prestige tier · costs more than 88% of the 347 masks and treatments we’ve priced
Best for hair types
All types Nothing in the formula or the claims narrows this to one pattern. Your hair
All types Nothing in the formula or the claims narrows this to one pattern. Your hair
Moisture level Same
High Humectants near the top — water-binding is a headline mechanism here. Your hair
High Humectants near the top — water-binding is a headline mechanism here. Your hair
Oils and butters Same
None No oils or butters in the list. Your hair
None No oils or butters in the list. Your hair
Slip / detangling Same
High Conditioning agents sit high in the list — this is a detangling formula. Your hair
High Conditioning agents sit high in the list — this is a detangling formula. Your hair
Weight on hair
Medium Middle of the range — noticeable on fine hair, light on coarse hair. Your hair
—
Fragrance
Present Fragrance is listed; it sits below the working ingredients. Your hair
Present Fragrance is listed; it sits below the working ingredients. Your hair
Protein Same
Prominent Protein high in the list — a strengthening formula, not a moisture one. Your hair
Prominent Protein high in the list — a strengthening formula, not a moisture one. Your hair
Silicone / wax buildup Same
None Nothing here needs a detergent wash to remove. Your hair
None Nothing here needs a detergent wash to remove. Your hair
Clarifying wash needed
Low Your hair
Low Your hair
Formula completeness
out of 10
Covers the core
out of 10
Covers the core
Who should choose this
  • Protein-hungry hairthat stretches and stays stretched when wet
  • Maximum slipfor hair that tangles the moment it is wet
  • Dry, thirsty hairhumectants and emollients both sit up front
  • Curly-method routinesno sulfates and no water-insoluble silicones
  • Protein-hungry hairthat stretches and stays stretched when wet
  • Maximum slipfor hair that tangles the moment it is wet
  • Dry, thirsty hairhumectants and emollients both sit up front
  • Short ingredient listsfifteen ingredients or fewer
Why you might skip it
  • Scents bother youthis product carries a scent
  • Protein-sensitive hairthat goes stiff or straw-like on protein
  • Very dry or damaged hairit contains fast-drying alcohol
  • Scents bother youthis product carries a scent
  • Protein-sensitive hairthat goes stiff or straw-like on protein
  • Dry or very humid airwhere heavy humectants work against you
from the formula stated by the brand reported by reviewers Scale: 1 dot low · 5 dots high, within this product type.
More facts about each one
Type
Mask / treatment
Mask / treatmentcream
Where to buy
Salons · Grocery / mass
Salons · Specialty beauty
Free of
  • sulfate-free
  • silicone-free
  • curly-method compatible
—
Vegan
Vegan · label states
—
Cruelty-free
Cruelty-free · label states
Cruelty-free · PETA-listed
Scent
Scented, not described
Scented, not described

Facts as we recorded them. A dash means we have not researched that field for that product — it is not a "no".

The bottom line

The bottom line depends on your hair

Which of these two suits you is a question about your hair, not about them. The consultation answers it — and tells you what your routine needs around it.

Take the consultation

$49.00 once, for your consultation and hair profile. No subscription, no required purchases.

The detail behind the table

Where the readings above come from: the ingredient lists themselves, each brand’s claims checked against them, what owners report, and cost per ounce in context.

Shared and distinct ingredients

Shared and distinct ingredients

Computed from the ingredient lists as printed. "Shared" means both lists carry it; where it sits on each label is stated, because position is what tells you how much.

What both formulas carry

IngredientPro Molecular Repair Hair MaskBond Rx Step 1 Professional Bond Builder
Water
Neutral
#1Leading
#1Leading
Propylene Glycol
Moisturizes
#3Leading
#4Supporting
Cetearyl Alcohol
Softens
#4Supporting
#2Leading
Behentrimonium Chloride
Detangles
#7Supporting
#3Leading
Fragrance
Fragrance
#17Below the 1% line
#11Below the 1% line

What only one of them carries

Pro Molecular Repair Hair Mask

Bond Rx Step 1 Professional Bond Builder

Full ingredient list — Pro Molecular Repair Hair Mask (23)
Full ingredient list — Bond Rx Step 1 Professional Bond Builder (11)

Claims check

What each brand says, against what each formula shows

Claims are quoted from each brand. We only mark one supported, partly supported, or conflicting when that product’s ingredient list actually speaks to it.

VerdictsPro Molecular Repair Hair MaskBond Rx Step 1 Professional Bond Builder
Supported
3
4
Partly supported
0
0
Stated by brand
3
1
Potential conflict
0
0

Pro Molecular Repair Hair Mask

  • Reverses damage as the second step of the K18REPAIR professional serviceSupportedReinforces a damaged strand.
  • Repairs damage from bleach, color, chemical services and heatSupportedReinforces a damaged strand.
  • Reconnects broken polypeptide chains and disulfide bondsSupportedReinforces a damaged strand.
  • Restores elasticity and strength in 4 minutesStated by brandCan’t be confirmed from label.
  • Clinically proven damage reversalStated by brandOnly the brand’s testing shows this.
  • Works on all hair typesStated by brandSee the fit panel instead.

Bond Rx Step 1 Professional Bond Builder

  • designed to transform any lightening or hair color service into a powerful bond-building treatmentSupportedReinforces a damaged strand.
  • addresses breakage, brittleness, and damage caused by chemical treatmentsSupportedReinforces a damaged strand.
  • contains bonding agents, amino acids, and proteinsSupportedReinforces a damaged strand.
  • designed to be used on all hair types and colorsStated by brandSee the fit panel instead.
  • retains 85 percent of disulfide bonds while lightening (Step 1 + Step 2, vs. virgin hair)SupportedReinforces a damaged strand.

What owners say

What people report

Recurring themes our researchers wrote in their own words from sourced reviews. We do not store or scrape star ratings, and we never balance one product’s themes against another’s by inventing them.

Pro Molecular Repair Hair Mask

Stylists frequently describe visibly repairing severely damaged or over-processed hair, especially on blonde and lightened clients, within a single treatment.

Reviewers commonly describe the result as hair that feels noticeably stronger, shinier and softer right after the four-minute application.

Many reviewers say their clients specifically ask for this treatment again after their first experience with it.

Bond Rx Step 1 Professional Bond Builder

No review themes researched for this product yet.

Price check

Cost per ounce, in context

Cost per ounce against every product of this type we have priced, each at the size it is most often sold in. Value labels are computed from that percentile and from how many products that do the same job cost less; they are comparisons, not judgements about a brand.

$8.29/oz vs $13.83/oz — K18 Pro Molecular Repair Hair Mask costs about 1.7× more per ounce than Paul Mitchell Bond Rx Step 1 Professional Bond Builder.

$0.19/oz median $3.49/oz $24.50/oz $13.83/oz Pro Molecular Repair Hair $8.29/oz Bond Rx Step 1 Professiona

Every mark sits on one distribution because these are compared against the same set: 347 masks and treatments with a computable unit price.

Value readPro Molecular Repair Hair MaskBond Rx Step 1 Professional Bond Builder
Label
Same job for less elsewhereYou are paying above the range for a formula close to several lower-priced options.
Same job for less elsewhereYou are paying above the range for a formula close to several lower-priced options.

Computed from cost per ounce against every product of this type we have priced, and from how many products that do the same job cost less. It is a comparison, not a judgement about the brand.

Compare with something else

Close formulas to each of these, as their own comparison pages.

Pro Molecular Repair Hair Mask vs Dualsenses Bond Pro 60sec TreatmentGoldwell · 95% function matchBond Rx Step 1 Professional Bond Builder vs Extreme CAT Anti-Damage Protein Reconstructing Rinse-Off TreatmentRedken · 99% function matchPro Molecular Repair Hair Mask vs 8 Second Wonder Water Lamellar Hair TreatmentL'Oreal Paris Elvive · 92% function matchBond Rx Step 1 Professional Bond Builder vs Dualsenses Bond Pro 60sec TreatmentGoldwell · 93% function matchPro Molecular Repair Hair Mask vs Extreme CAT Anti-Damage Protein Reconstructing Rinse-Off TreatmentRedken · 90% function matchBond Rx Step 1 Professional Bond Builder vs 8 Second Wonder Water Lamellar Hair TreatmentL'Oreal Paris Elvive · 92% function matchPro Molecular Repair Hair Mask vs Puremix Wild Honey Repairing MaskRusk · 90% function matchBond Rx Step 1 Professional Bond Builder vs EverPure Sulfate Free Bond Repair+ Pre-Shampoo TreatmentL'Oreal Paris Elvive · 86% function match

Pro Molecular Repair Hair Mask · Bond Rx Step 1 Professional Bond Builder · All masks and treatments in the library

How this page was made

  • This page is assembled from the same researched records the individual product pages render: identity, each ingredient list as printed, each brand's own claims, dated price observations, and review themes written in our researchers' own words. Nothing on it is written per comparison.
  • We do not rank these against each other. Which of them suits you depends on your hair, and that is what the consultation works out.
  • The formula similarity percentage is a stored, precomputed number: position-weighted overlap of the two ingredient lists blended with agreement on the attributes we derive. It measures how alike two formulas are, not how well either works.
  • 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.
  • 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.
  • 6 sources were consulted across the products on this page.
  • Ingredient order tells you relative amount only above roughly 1%. Prices are observations on the dates shown and change without notice. We do not sell these products and take no placement fees.
  • This is cosmetic information, not medical advice, and nothing here diagnoses or treats a health condition.

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