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4.7
Rated 4.7 out of 5 stars
8,983 Reviews

jumbo leave-in molecular repair hair mask

4-minute leave-in treatment to reverse hair damage - now in an exclusive jumbo size
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
  • 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.

  1. Shampoo, do not condition. Towel-dry thoroughly.
  2. Apply 1-3 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.
  • 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
limited edition
K18 x Future Society leave-in molecular hair mask
4.9
Rated 4.9 out of 5 stars
84 Reviews
Bestselling mask scented with Floating Forest biotech fragrance
K18 molecular repair hair oil
4.8
Rated 4.8 out of 5 stars
993 Reviews
Weightless oil that strengthens, repairs damage + reduces frizz

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.

powered by K18PEPTIDE™

Biomimetic peptide clicks into hair’s keratin structure—the source of core strength—for soft, shiny, bouncy results that won’t wash away.

how to use molecular repair mask
1. Shampoo, do not condition. Towel-dry thoroughly.

2. Apply 1-3 pumps 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 styling product + style as usual. Use for 4-6 washes, then as needed.


*k18hair.com/disclaimers
learn more on our blog
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 8,983 reviews
93%would recommend these products
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.
Customers Talked About
8,983 reviews
  • Nataliya M.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Frizz, Color-care, Dryness, Fragile/brittle hair
    Hair Type Medium Density
    My Results Less Frizz, Stronger Hair, Smoother Hair, Less Breakage, Soft Touchable Hair
    Rated 5 out of 5 stars
    4 minutes ago
    The product is of excellent quality. I will buy again.

    The product is of excellent quality. I will buy again.

  • Jen W.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 25 - 34
    Hair Concern Fragile/brittle hair, Split-Ends, Dryness, Chemical damage, Frizz
    Hair Type Medium Density
    My Results Less Frizz, Visible Difference, Stronger Hair, Less Breakage, Smoother Hair
    Rated 5 out of 5 stars
    1 week ago
    Saving my blonde hair

    I really do believe this is making my bleached hair stronger. My hair at the top of my head feels stronger while the bottom from previous bleach damage is fragile. But as it’s growing out I feel like becoming healthier and stronger. I believe I can still be blonde and have long hair with this product.

    K Profile picture for K18Hair
    K18Hair
    6 days ago

    Thank you so much, Jen! We're absolutely thrilled to hear the Jumbo Leave-In Molecular Repair Hair Mask is helping strengthen your bleached hair and giving you hope for maintaining healthy, long blonde hair! It's amazing that you're already noticing the difference in strength as your hair grows out. Your support and trust in our products means the world to us ✨

  • Paige H.
    Verified Buyer
    Reviewing
    Jumbo Leave-In Molecular Repair Hair Mask 100mL
    I recommend this product
    Age 25 - 34
    Hair Concern Heat damage, Fragile/brittle hair, Dryness, Color-care
    Hair Type Straight/Wavy, Thick/Coarse
    My Results Visible Difference, Stronger Hair, Soft Touchable Hair
    Rated 5 out of 5 stars
    1 week ago
    Game changer

    My hair was not growing (breaking off) for YEARS and after just a few uses my hair was restored and I am a forever customer!

    K Profile picture for K18Hair
    K18Hair
    6 days ago

    Thank you so much, Paige! We're absolutely thrilled to hear the Jumbo Leave-In Molecular Repair Hair Mask has been such a game changer for your hair growth and breakage issues. It means the world to us to know we've helped restore your hair after years of struggle. Welcome to the K18 family — we're so grateful to have you as a forever customer!

  • Kate S.
    Verified Buyer
    Reviewing
    K18 x Future Society Limited Edition Scent Mask
    I recommend this product
    Age 35 - 44
    Hair Concern Heat damage, Color-care, Dryness, Split-Ends
    Hair Type Medium Density, Straight/Wavy
    My Results Visible Difference, Stronger Hair, Less Breakage, Soft Touchable Hair, Shinier Hair
    Rated 5 out of 5 stars
    1 week ago
    The best to keep my long hair healthy

    I use 2x per month to keep my hair healthy in the hot/sunny/dry Colorado summers

    K Profile picture for K18Hair
    K18Hair
    1 week ago

    Thank you for sharing your experience, Kate! We're so happy to hear the K18 x Future Society Limited Edition Scent Mask is helping keep your long hair healthy through those hot Colorado summers. Using it twice a month sounds like the perfect routine — we truly appreciate your support!

  • Fabiola J.
    Verified Buyer
    Reviewing
    Mini Leave-In Molecular Repair Hair Mask 15 mL
    I recommend this product
    Age 45 - 54
    Hair Concern Chemical damage, Frizz
    Hair Type Fine/Thin
    My Results Visible Difference
    Rated 5 out of 5 stars
    1 week ago
    I love

    It really is a good product.

    K Profile picture for K18Hair
    K18Hair
    1 week ago

    Thank you so much for this wonderful review, Fabiola! We're absolutely thrilled to hear that you love the Mini Leave-In Molecular Repair Hair Mask and that you're experiencing what a good product it really is! That's exactly what we love to hear! We're so excited that you're loving the results and thanks for your fantastic 5-star review! 💛

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