Skincare · reviewed

K18 Leave-In Molecular Repair Hair Mask
vs BondiBoost Rapid Repair Bond Builder+ Leave-In Hair Mask

The buying question

How do the listed key actives, disclosed percentages and fragrance listing differ?

Important differences

Same on 1 of 2 features checked

Both are fragranced leave-in hair masks, but K18's highlighted K18PEPTIDE is not in BondiBoost's ingredient list; BondiBoost highlights a different plant-based bond blend plus niacinamide and biotin. K18 is $75 for 50 mL; BondiBoost is $33 for 3.38 fl oz.

Equivalent performance is not established.

How we reached this verdict ↗

Original

K18

K18 Leave-In Molecular Repair Hair Mask — 50 mL

$75.00US price

$150.00 / 100 mL

Checked Oct 28, 2026, 4:35 PM EDT

Alternative

BondiBoost

BondiBoost Rapid Repair Bond Builder+ Leave-In Hair Mask — 3.38 oz

$33.00US price

$33.01 / 100 mL

Checked Oct 28, 2026, 4:48 PM EDT

Same, partial, different, unknown.

“Same” means a recorded feature matches, not equivalent performance.

Listed key actives and disclosed percentages

Different

Original: K18PEPTIDE: percentage undisclosed; Brand-stated
Alternative: K18PEPTIDE: Absent from full ingredient list (0%); Bond Builder+ Technology (hydrolyzed soy protein, onion and ginseng extracts, vitamin B, amino acids): percentage undisclosed; Polycare Split Therapy Technology (guar-derived): percentage undisclosed; Aloe vera: percentage undisclosed; Niacinamide: percentage undisclosed; Biotin: percentage undisclosed; Brand-stated

K18 highlights a single active, its K18PEPTIDE; the only peptide in K18's ingredient list is sh-Oligopeptide-78. Neither appears in BondiBoost's list. BondiBoost instead highlights a plant-based "Bond Builder+" blend, a guar-derived split-end ingredient, aloe vera, niacinamide and biotin; none of these appear in K18's list. Both lists include hydrolyzed wheat protein. Neither brand discloses amounts.

Sources

Original: K18 US product page (description and ingredient list); Checked Oct 28, 2026; K18 names K18PEPTIDE as the mask's active. Its ingredient list includes sh-Oligopeptide-78, the only peptide listed. No percentage appears on the K18 or Sephora pages.
Alternative: BondiBoost US product page (key ingredients and full ingredient list); Checked Oct 28, 2026; K18PEPTIDE is not listed in BondiBoost's full ingredient list, and neither is sh-Oligopeptide-78 or any other oligopeptide, so it is recorded as 0%. The other five are the ingredients BondiBoost highlights on its page; it gives no percentages.

Fragrance listed

Same

Original: Yes; Brand-stated
Alternative: Yes; Brand-stated

Both ingredient lists include fragrance: "Fragrance (Parfum)" for K18 and "Parfum/Fragrance" for BondiBoost.

Sources

Original: K18 ingredient list; Checked Oct 28, 2026
Alternative: BondiBoost ingredient list; Checked Oct 28, 2026

Stated product format

Same

Original: Leave-in hair mask; Brand-stated
Alternative: Leave-in hair mask; Brand-stated

Both are leave-in masks applied to damp hair after shampooing and not rinsed out. Each brand's directions say to leave it on for 4 minutes (K18) or at least 4 minutes (BondiBoost) before styling.

Sources

Original: K18 US product page; Checked Oct 28, 2026
Alternative: BondiBoost US product page; Checked Oct 28, 2026

Outside this verdict’s scope; included for context.

What we couldn’t check

Listed key actives and disclosed percentages. Neither brand discloses ingredient percentages. BondiBoost's page also highlights "squalane & plant oils" and "peptides & proteins"; its full ingredient list includes plant oils and hydrolyzed soy and wheat proteins, but no ingredient named squalane or peptide.
Comparative performance. Damage repair, how hair feels and how long results last have not been compared. Both brands say their mask reverses damage in 4 minutes; those are their claims.