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Leave-in molecular repair hair mask 15mL
get stronger, more resilient hair. left - 8x bleach without K18, right 8x bleach with K18
Red curly hair before and after results using k18.
Grey curly hair before and after results using k18.
Red curly hair before and after results using k18.
Bleach blonde hair before and after results using k18.
get stronger, more resilient hair. left - 8x bleach without K18, right 8x bleach with K18
where K18 molecular repair works
the K18 routine
maximze your repair
less is more
works for all hair types
where does K18 fit into your routine?
Mini versus full size product comparison
K18 routine guide
4.7
Rated 4.7 out of 5 stars
8,263 Reviews

mini leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage
OR

Description

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥 

*Disclaimers

Repairs Damage Caused By

  • Bleach + Color
  • Heat
  • Chemical Services
  1. Shampoo, do not condition. Towel-dry thoroughly.
  2. Apply 3-9 pumps of K18 leave-in molecular repair hair mask based on your length and density, starting at the ends and working up towards the roots.
  3. Let sit for 4 minutes. Do not rinse out.
  4. Comb, add product + style as usual. Use for 4-6 washes post-salon service, then as needed.
  • K18PEPTIDE™is a biotech-developed peptide that mimics hair's structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during bleaching, color and chemical services + heat*.

  • pH-optimized (5.0-6.0) to help minimize cuticle swelling + put hair proteins in their most resilient state.

  • Cream format enables easy, lightweight application across all hair types, with detangling and softening benefits.

  • Vegan, color-safe, cruelty-free.

Takes damage repair further – reconnects both polypeptide chains (and as a result, also reconnects disulfide bonds) for strength along the length + width of the hair - offering comprehensive, lasting damage repair.

Restores hair from even extreme damage - by working at the innermost layer of the hair, core strength and elasticity are renewed for strong, smooth, bouncy hair.

Delivers immediate and lasting results – hair is repaired from the first use and lasts past your next wash, for ongoing reparative benefits.

Simplified repair - convenient, leave-in formula works in just 4 minutes, with no extra rinse required.

Works on all hair types – because K18PEPTIDE™ works on a molecular level (where all hair is the same), this product is effective on all hair types.

  • DO clarify before K18 if you’re a heavy product user (demineralize for mineral + metal buildup).
  • DO apply on clean, damp hair.
  • DO wait the full 4 minutes before combing or styling.
  • DO add whatever styling products you love after the 4 minutes.
  • DO use for 4-6 shampoos consecutively for progressive results.
  • DON'T use conditioner before applying K18 Mask (you can apply after the 4 min but most find they don’t need it).
  • DON'T overdo it—less is more.
  • DON'T rinse it out.

Water (Aqua) (Eau), Alcohol Denat., Propylene Glycol, Cetearyl Alcohol, Dicaprylyl Ether, Cetyl Esters, Behentrimonium Chloride, Polysorbate 20,sh-Oligopeptide-78 (K18PEPTIDE™), Hydrolyzed Wheat Protein, Hydrolyzed Wheat Starch, Isopropyl Alcohol, Tocopherol, Phenoxyethanol, Potassium Sorbate, Citric Acid, Fragrance (Parfum), Geraniol, Linalool, Hexyl Cinnamal, Benzyl Alcohol.

pairs well with
K18 molecular repair hair oil
4.8
Rated 4.8 out of 5 stars
802 Reviews
Weightless oil that strengthens, repairs damage + reduces frizz
PEPTIDE PREP™ detox shampoo
4.9
Rated 4.9 out of 5 stars
517 Reviews
Color-safe, non-stripping clarifying shampoo with the K18PEPTIDE™

Description

A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair.

20+ billion TikTok views 🔥 

*Disclaimers

got questions?
Get started here.
The K18 mask works as a treatment to reverse damage in 4 minutes. It’s powered by our biomimetic K18PEPTIDE™ to seamlessly fit in and reconnect broken polypeptide chains at the molecular level. As a result, disulfide bonds are also reconnected for reinforced strength along the length + width of hair—offering comprehensive, lasting, and progressive repair.
K18PEPTIDE™ is a biotech-developed peptide that mimics hair’s structure to reverse damage by reconnecting polypeptide chains and disulfide bonds broken during damage from bleach + color, chemical services, and heat*
*Disclaimers
Conditioner leaves a film that blocks our peptide from penetrating effectively. Once the 4-minute wait time is up, feel free to use a conditioner, a leave-in, or any type of product.
We like to keep our formulas minimal, only using the exact amount of ingredients needed to get the peptide where it needs to go. Here the alcohol serves as an agent to optimize the hair environment for the K18 mask to work on a deeper level. Our unique blend of 3 alcohols functions to open the hair cuticle so the K18PEPTIDE™ can penetrate the innermost layer of hair, reaching the broken polypeptide chains (keratin chains).
Most see results after 2-3 uses. The more damaged the hair, the more dramatic the results so it may vary depending on your hair type and level of damage.
Straight bleached hair after using K18 mask.
Straight bleached hair before using K18 mask.

healthier hair with every use

Reverse damage in 4 minutes with our breakthrough K18 molecular repair technology.
the K18 difference
Feel what’s possible with fewer steps, less waste + less time.
efficacy
patented K18PEPTIDE™ powers deeper + lasting repair.
simplicity
fewer steps for a streamlined routine.
speed
results in one 4-minute use.
how molecular repair compares
how K18 works

Traveling into the innermost layers of hair, our K18PEPTIDE™ renews strength along the width AND length of hair for lasting strength where it matters.

feel what's possible with K18
See how K18 unlocks our community's expression
4.7
Rated 4.7 out of 5 stars
Based on 8,263 reviews
Reviews Summary
Customers say this leave-in hair mask transforms their hair texture and manageability after just one use. Many reviews mention noticeable improvements in softness and reduced frizz. Users with curly, fine, and color-treated hair report positive results. The mask works well for various hair types, with many noting improved texture and easier styling. While some mention the product's high price point, most find a little goes a long way. A few users recommend using conditioner alongside the mask for best results. Reviews consistently highlight the mask's effectiveness for addressing dry, brittle hair concerns.
8,263 reviews
  • Denise B.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 55 - 64
    Hair Concern Chemical damage, Frizz, Dryness, Extending time between washes
    Hair Type Grey Hair, Straight/Wavy, Medium Density
    My Results Less Frizz, Visible Difference, Stronger Hair, Smoother Hair, Shinier Hair
    Rated 5 out of 5 stars
    10 hours ago
    Magic in a bottle

    This product has transformed my hair!

    Why did it take me 60 years to discover it??

  • Britteny B.
    Verified Buyer
    Reviewing
    Leave-In Molecular Repair Hair Mask Sample
    I recommend this product
    Rated 5 out of 5 stars
    2 days ago
    loved it

    worked so well for my hair saw result immediately

    K Profile picture for K18Hair
    K18Hair
    Yesterday

    So happy to hear you loved the Leave-In Molecular Repair Hair Mask Sample and saw immediate results, Britteny! Thanks for the wonderful 5-star review!

  • Wesley K.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 35 - 44
    Hair Concern Chemical damage, Color-care
    Hair Type Medium Density
    My Results Visible Difference, Less Breakage, Smoother Hair, Stronger Hair
    Rated 5 out of 5 stars
    1 month ago
    The Secret Behind Santa's Bright White Beard — K18 Delivers!

    As a professional Santa Claus, keeping my beard bright, healthy, and picture-perfect is part of the magic. But constant bleaching to maintain that iconic white beard takes a toll—and not even the North Pole’s best elves can fix damage like that!

    Over the years, I’ve tested just about every product out there to repair breakage, soften coarse hair, and protect my beard (and hair) from the effects of bleach and hard water. Nothing has worked as well as the K18 Leave-In Molecular Repair Hair Mask.

    Here’s why it’s become my go-to:

    ✔️ Repairs damage from bleaching—noticeably stronger, healthier hair

    ✔️ Softens coarse beard hair—essential for those magical holiday photos

    ✔️ Lightweight, no greasy feeling—perfect for daily use

    ✔️ Simple routine—apply to towel-dried hair, wait 4 minutes, style and go

    The truth is, children believe in Santa—and the beard is a huge part of that magic. With K18, I can keep my beard looking bright and healthy, season after season.

    And just to be clear—this isn’t a sponsored review. I’m a real customer, and K18 has made a real difference for my beard, my hair, and my confidence.

    If you bleach, color, or struggle with damage, do yourself a favor—K18 truly works miracles.

    K Profile picture for K18Hair
    K18Hair
    1 month ago

    Thank you, Wesley! Santa needs healthy hair and a healthy beard! We appreciate your review!

  • Leis T.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 45 - 54
    Hair Concern Color-care, Heat damage, Dryness
    Hair Type Medium Density
    My Results Visible Difference, Less Breakage, Smoother Hair, Shinier Hair, Less Frizz
    Rated 4 out of 5 stars
    1 month ago
    Excellent performance 👏

    I am so happy I found this. What a difference it makes ..

    K Profile picture for K18Hair
    K18Hair
    1 month ago

    Thank you for your support and for choosing K18 for your hair care needs.

  • Niav H.
    Verified Buyer
    Reviewing
    Full-Size Leave-In Molecular Repair Hair Mask 50mL
    I recommend this product
    Age 35 - 44
    Hair Concern Extending time between washes, Fragile/brittle hair, Color-care
    Hair Type Fine/Thin, Straight/Wavy
    My Results Soft Touchable Hair, Cleaner, fresher hair, Bouncy Hair, Visible Difference, Oil absorbed
    Rated 5 out of 5 stars
    1 month ago
    Love this product

    I have been loving using this product. It works as advertised. 4 pumps after shampooing only. My hair is in better shape after several weeks of using

    K Profile picture for K18Hair
    K18Hair
    1 month ago

    We’re so happy K18 is bringing your hair back to life, thank you for trusting us with your strands!

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