★★★★★
My tech noticed before I said anything.
By my third fill she asked what changed. I hadn't told her about the serum yet.
— Mira N., Verified Customer
One serum. Built for the lash extension lifestyle.
KØS brings peptide science into a formula made to work with your fills, not against them — so every appointment builds on stronger lashes, not thinner ones.
Explore KØS
- 30-Day Risk-Free Trial
- Extension-Safe Formula
- Ships in 24 Hours
The Only Step
KØS Lash Serum
One daily peptide serum, built to work with your fill schedule instead of against it — so every appointment builds on stronger lashes, not thinner ones.
$47
Explore KØS- Extension-Safe
- 60 Seconds a Day
- 30-Day Guarantee
The lash line is the most delicate — and most neglected — stretch of skin on the face.
— common wisdom among certified lash technicians
The lash industry forgot something
Extensions got a lot more sophisticated. Aftercare didn't.
Walk into any lash studio and you'll find incredible technique — volume sets, hybrid fills, lash mapping down to the millimeter. What you won't find is much conversation about what's happening to the natural lash underneath, fill after fill.
Most 'growth serums' weren't built with extensions in mind at all — half of them aren't even safe to use over a fresh fill. KØS was built specifically for people who have no plans to stop getting extensions, ever.
★★★★★
Finally, extension-safe.
Every other serum I tried had oils that made my tech nervous. This one she actually approved.
— Sofia R., Verified Customer
★★★★★
Fills last longer now too.
More natural lash for the extension to actually hold onto — wasn't expecting that side effect.
— Priya K., Verified Customer
★★★★★
60 seconds, that's genuinely it.
Fits into the routine I already had. No extra step, no waiting to reapply extensions.
— Hana T., Verified Customer
What our customers are saying
Fill 1 → Fill 3 diary
My tech's reaction
60-second routine
Extension-safe test
Unboxing + first use
30-day check-in
Does this sound like you?
Different reasons, same fix — here's where KØS actually helps.
Your natural lashes feel thinner than they used to
Gaps, sparse patches, or shedding you've noticed since starting extensions.
See how KØS helps →Your fills don't last as long as they should
Extensions falling out early because there's less natural lash to hold onto.
See how KØS helps →You're just starting extensions and want to stay ahead of it
No damage yet — this is the easiest time to build the habit before there's anything to fix.
See how KØS helps →What people typically spend instead
Fixing lash damage the old way adds up fast.
Lash-strengthening treatment at the salon$65
Generic growth serum (non-extension-safe)$40
Extra fill visit from early extension loss$55
Lash vitamins / supplements$25
Typical monthly spend$185
vs.
KØS Lash Serum
$47
Roughly $138 less than the alternatives — one bottle, no subscription
One formula, built specifically for the fill cycle — extension-safe, peptide-driven, no separate treatments needed. One-time purchase, lasts about a month.
Explore KØSThousands of 5-Star Reviews · Rated 4.9 ★
See what our customers are saying about KØS
★★★★★
You can actually see it working.
By the second fill my tech pointed it out before I said anything. Genuinely didn't expect that.
Mira N.Verified Customer
Fill Retention · Fuller Lash Line
★★★★★
Finally one that's actually extension-safe.
Two other serums I tried weren't safe over fresh fills. My tech gave this one the okay immediately.
Sofia R.Verified Customer
Extension-Safe · Daily Routine
★★★★★
Worth it just for the fill retention.
My extensions genuinely last longer now — more real lash underneath for them to hold onto.
Priya K.Verified Customer
Fill Retention · Long-Term Results
Frequently Asked Questions
Is KØS actually safe to use with lash extensions?
Yes — KØS is formulated without oils or silicones known to break down lash adhesive, so it's safe to apply the same day as a fill.
How is this different from a regular lash growth serum?
Most growth serums weren't designed around a fill cycle at all. KØS is built specifically to work in the 2–3 week window between appointments, without interfering with the bond.
How long until I see results?
Most customers notice a difference by their second fill, with fuller results building through the third fill cycle.
What's your guarantee?
Every order comes with a 30-day money-back guarantee. If you don't see a difference, send it back for a full refund — no questions asked.