Jumbo leave in molecular repair hair mask

Mini, Full, and Jumbo size leave in molecular repair masks lined up next to each other on a pink background.

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

Jumbo Leave-In Molecular Repair Hair Mask 100mL

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4.7

Rated 4.7 out of 5 stars

8,131 Reviews

jumbo leave-in molecular repair hair mask

Name: Jumbo Leave-In Molecular Repair Hair Mask 100mL
Brand: K18Hair
SKU: K18-31008
Price: 120.00 GBP
Availability: InStock

4-minute leave-in treatment - now in an exclusive jumbo size

Jumbo Leave-In Molecular Repair Hair Mask 100mL £120.00

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

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.

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.

how to use

Shampoo, do not condition. Towel-dry thoroughly.
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.
Let sit for 4 minutes. Do not rinse out.
Comb, add product + style as usual. Use for 4-6 washes post-salon service, then as needed.

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.

ingredients

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

PEPTIDE PREP™ detox shampoo

4.9

Rated 4.9 out of 5 stars

547 Reviews

Color-safe, non-stripping clarifying shampoo with the K18PEPTIDE™

Molecular repair hair oil

4.8

Rated 4.8 out of 5 stars

950 Reviews

Weightless oil that strengthens, repairs damage + reduces frizz

Description

20+ billion TikTok views 🔥

*Disclaimers

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*

*k18hair.co.uk/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 coloUring 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. Most of the product leave my hair greasy and I can’t even style it, and right after washing I have to put it in the bun. It’s a nightmare! But not with k-18. 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

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.

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 8,131 reviews

93%would recommend these products

Reviews Summary

Customers say this hair mask transforms damaged, bleached, and chemically-treated hair, making it softer, stronger, and more manageable. Many report significant improvements in hair texture, with reduced breakage, split ends, and frizz. Users with curly hair find it enhances curl definition and reduces dryness. The lightweight formula doesn't weigh hair down or leave residue. Many reviews mention it works particularly well for bleached hair, helping restore smoothness and shine. Some note the price is high but find it worthwhile since only small amounts are needed per use.

Customers Talked About

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8,131 reviews

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Dena F.
Verified Buyer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Age 18 - 24
Hair Concern Split-Ends
Hair Type Fine/Thin
My Results Less Frizz, Visible Difference, Less Breakage, Smoother Hair
Rated 5 out of 5 stars
4 hours ago
Good stuff
I have very baby fine hair. I have been struggling to find a shampoo and conditioner that will make my hair look, soft and shiny and not weighed down and drab. I've only been using this for two weeks so far so good definite improvement in the texture my hair softer and shinier. I can't use the hair oil because it's too heavy for my hair., I will keep working with it. The molecular hair oil works really well from my daughter's hair and my son. I love how this company gives out decent samples too. It's such a good way to share with other people and then try the product before you wired to see if it works well for you or not.
Was this helpful?
KU
K18Hair UK
3 hours ago
Thank you for the wonderful review! We're so happy to hear the Molecular Repair Hair Mask is making your fine hair softer and shinier. Thanks for sharing your experience!
Lilia H.
Verified Buyer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Age 35 - 44
Hair Concern Chemical damage, Color-care, Frizz, Dryness
Hair Type Thick/Coarse
My Results Stronger Hair, Visible Difference, Less Frizz, Smoother Hair, Soft Touchable Hair
Rated 5 out of 5 stars
2 days ago
1st noticed difference
Had drastic issues with my hair after my last bleach and a previous hairstylist recommended this product. I instantly noticed a change in my hair after first use. My natural curls are back. Excited to see the results after more uses.
Was this helpful?
KU
K18Hair UK
2 days ago
Thank you for your amazing review, Lilia! 💛 We're thrilled the Leave-In Molecular Repair Hair Mask brought your natural curls back after bleach damage. Excited for your continued results! ✨😊
Heather H.
Verified Buyer
Reviewing
Jumbo Leave-In Molecular Repair Hair Mask 100mL
I recommend this product
Age 25 - 34
Hair Concern Heat damage, Chemical damage, Fragile/brittle hair, Dryness, Split-Ends
Hair Type Thick/Coarse, Curly/Coily
My Results Visible Difference, Stronger Hair, Less Breakage, Smoother Hair, Defined Curl/Wave Pattern
Rated 5 out of 5 stars
4 days ago
Amazing
The one item I will splurge on and purchase over and over. The only thing that has saved my bleached hair. Well worth the price
Was this helpful?
KU
K18Hair UK
2 days ago
Thank you for your amazing review, Heather! 💛 We're so thrilled to hear that the Jumbo Leave-In Molecular Repair Hair Mask has become your go-to splurge and is saving your bleached hair. It means the world to us to know that K18 has earned such a special place in your routine! Thank you for your continued support and for sharing your experience with us. ✨😊
Kayla H.
Verified Buyer
Reviewing
Jumbo Leave-In Molecular Repair Hair Mask 100mL
I recommend this product
Age 25 - 34
Hair Concern Chemical damage, Dryness
Hair Type Straight/Wavy
My Results Less Breakage, Smoother Hair
Rated 5 out of 5 stars
4 days ago
love!!
my hair has been bleached multiple times and instantly feels better as soon as this mask touches it :’) finally starting to be able to grow my hair out healthily !!
Was this helpful?
KU
K18Hair UK
2 days ago
Thank you for the incredible review! We're so thrilled to hear the Jumbo Leave-In Molecular Repair Hair Mask is helping your bleached hair feel better and that you're finally able to grow it out healthily. There's nothing better than seeing damaged hair transform! We appreciate you sharing your experience and for being part of the K18 community!
Christina N.
Verified Buyer
Reviewing
Full-Size Leave-In Molecular Repair Hair Mask 50mL
I recommend this product
Rated 5 out of 5 stars
1 week ago
Great product
So easy to use light and not sticky. I’ve noticed less hair fall out and receive many comments on how healthy my hair look and asked what I use.
Was this helpful?
KU
K18Hair UK
6 days ago
Thank you so much, Christina! We're thrilled to hear the Leave-In Molecular Repair Hair Mask is working so well for you and that it feels light and non-sticky. It's amazing that you're experiencing less hair fall and getting compliments on how healthy your hair looks — that's exactly what we love to hear! ✨ Thank you for sharing your experience with us!