Leave-in molecular repair hair mask 50mL

Full-Size Leave-In Molecular Repair Hair Mask 50mL

Red curly hair before and after results using k18.

Grey 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

4.7

Rated 4.7 out of 5 stars

9,294 Reviews

bestseller

full-size leave-in molecular repair hair mask

Name: Full-Size Leave-In Molecular Repair Hair Mask 50mL
Brand: K18Hair
SKU: K18-31005
Price: 75.00 USD
Availability: InStock
Rating: 4.7 (9294 reviews)

4-minute leave-in treatment to reverse hair damage

Full Size - 50mL$75.00 Jumbo Size - 100mL$120.00 Mini Size - 15mL$29.00 Limited-Edition Scent - 50 mL$75.00

$75

View Full Details

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

- ingredients
  
  Water (Aqua) (Eau), Alcohol Denat., Propylene Glycol, Cetearyl Alcohol, Dicaprylyl Ether, Cetyl Esters, Behentrimonium Chloride, Polysorbate 20, sh- Oligopeptide-78, Hydrolyzed Wheat Protein, Hydrolyzed Wheat Starch, Isopropyl Alcohol, Tocopherol, Phenoxyethanol, Potassium Sorbate, Citric Acid, Fragrance (Parfum), Geraniol, Linalool, Hexyl Cinnamal, Benzyl Alcohol, Amyl Salicylate, Benzaldehyde.
- dos and don'ts
  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.
- key benefits
  
  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.
- more to know
  
  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.
- how to use
  
  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.

pairs well with

FutureIQ™ biomimetic hair longevity serum

PEPTIDE PREP™ detox shampoo

got questions?

Get started here.

how does the k18 mask work?

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.

what is the k18peptide™?

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

why skip conditioner?

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.

i noticed there’s alcohol in the formula, isn’t that bad for you?

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).

when should i expect to see results?

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.

soft, strong, bouncy hair for everyone

Repair damage for hair like new* in 4 minutes.

before

after

"I absolutely love this product!! You have to see it to believe it!"

- Christina Marie P.

before

after

“…I had my hair chopped (it was begging for it) along with some highlights and coloring of the roots. My hair stylist used this on my hair and I absolutely loved how it made my hair feel ... I love this mask so much!”

- Ashley P.

before

after

"Amazing the way it feels and the shine provides to the hair instantly."

- Sandra M.

before

after

"I’ve been using this mask for about four washes so far. I feel that my hair is getting healthier."

- Olga S.

before

after

"It makes my hair so soft and weightless, I absolutely love it... Makes my hair feel so luxurious, it’s like I just left the salon. Can’t recommend this product more!"

- Anastasiia T.

before

after

"My hair has been a mess for years... My new hair stylist recommended K18! ... My hair looks and feels amazing with lasting results!!"

- Arnell M

before

after

"I have heat damaged color treated curly hair and this has improved my hair health immensely...This is one of those products that has incorporated itself into my routine for the rest of my life..."

- Siria A.

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.

Explore the Science

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

October 24, 2024 / products

How much leave-in mask do you *really* need?

Find your optimal dose with this easy guide.

March 23, 2023 / hair science

The Science Behind K18 Molecular Repair

See how our K18PEPTIDE™-powered mask reverses damage in 4 minutes for lasting...

December 08, 2024 / products

The Top K18 Mask FAQs

answering your most-asked questions.

February 25, 2025 / products

molecular repair for curly + coily hair

looking to restore your natural curl pattern? you need K18.

February 06, 2025 / products

molecular repair for aging hair

Hair evolves with age. This is how to support your strands throughout the years.

View All

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 9,294 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

Write a Review (Opens in a new window)

9,294 reviews

Sort

Rickist
Verified Reviewer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Age 55 - 64
Hair Concern Heat damage, Fragile/brittle hair, Frizz, Dryness
Hair Type Fine/Thin
My Results Less Frizz, Stronger Hair, Smoother Hair, Visible Difference, Soft Touchable Hair
Rated 5 out of 5 stars
3 minutes ago
There's nothing like this
My hairdresser suggested this product, and it's amazing. I get my roots touched up monthly and add in high/low lights often. Aging is wreaking havoc on my hair, and it's getting fuzzier and finer by the minute. This product is the only one I've used that makes my hair more manageable. The price tag shouldn't scare you because the results are worth it (and you're worth it).
Was this helpful?
Catherine M. B.
Verified Buyer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Age 65+
Hair Concern Fragile/brittle hair, Dryness, Frizz
Hair Type Fine/Thin
My Results Visible Difference, Smoother Hair, Less Frizz
Rated 5 out of 5 stars
4 hours ago
works well
This mask is easy to use and produces very good results. Going to use it regularly from now on
Was this helpful?
K
K18Hair
3 hours ago
Thank you so much for the 5-star review, Catherine! We're thrilled to hear you're loving the Full-Size Leave-In Molecular Repair Hair Mask and that it's delivering such great results. 💙✨
Samantha P.
Verified Buyer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Age 35 - 44
Hair Concern Dryness, Frizz, Split-Ends, Heat damage
Hair Type Curly/Coily, Medium Density
My Results Less Frizz, Bouncy Hair, Visible Difference, Stronger Hair, Smoother Hair
Rated 5 out of 5 stars
4 hours ago
Instant results!
The way my hair instantly got hydrated simply after 3 pumps had me in a state of shock! And after styling, my hair was light and looking healthy!!
Was this helpful?
K
K18Hair
3 hours ago
Thank you so much for the love, Samantha! 💙 We're thrilled to hear you're getting instant results with our Full-Size Leave-In Molecular Repair Hair Mask! ✨
Katrina C.
Verified Buyer
Reviewing
Jumbo Leave-In Molecular Repair Hair Mask 100mL
I recommend this product
Age 18 - 24
Hair Concern Dryness, Frizz
Hair Type Fine/Thin
My Results Less Frizz, Smoother Hair, Soft Touchable Hair
Rated 5 out of 5 stars
15 hours ago
The best leave in conditioner
I love this product. It is smooth and creamy and perfect
Was this helpful?
K
K18Hair
14 hours ago
Thank you so much for the 5-star review, Katrina! We're thrilled you love our Jumbo Leave-In Molecular Repair Hair Mask. 💕 We truly appreciate your support! ✨
Lynn r.
Verified Buyer
Reviewing
K18 x Future Society Limited Edition Scent Mask
I recommend this product
Age 65+
Hair Concern Chemical damage, Frizz, Color-care
Hair Type Grey Hair, Curly/Coily
My Results Shinier Hair, Soft Touchable Hair, Smoother Hair, Visible Difference, Less Frizz
Rated 5 out of 5 stars
18 hours ago
Heavenly scent,incredible smoothing
Naturally curly, color treated blonde hair revived!!!
Was this helpful?
K
K18Hair
17 hours ago
Thank you so much for the love, Lynn! 💙 We're thrilled to hear the K18 x Future Society Limited Edition Scent Mask is reviving your curly, color-treated hair! ✨

*Disclaimers