Buy the Olaplex N°.9 Bond Protector™ Hair Serum.

Same heat protection, a formula that suits more hair types, and none of the salon markup.

What was compared

1. Same heat shield, a fifth of the price
Olaplex runs $10.67 per fluid ounce against Kerastase's $52, and both claim protection up to 450°F. You get the identical shield for a fraction of the spend, and the extra you'd pay Kerastase buys salon prestige, not better protection.
2. Fine hair won't get weighed down
Kerastase's cream is a hairdresser-flagged pick for medium to thick hair, not thin or fine strands. Olaplex's lightweight serum protects fine hair without the heaviness, so more people can actually wear it daily.
3. No silicone coating building up on hair
Olaplex's serum is silicone-free and vegan, so product absorbs instead of just sitting on the cuticle. Kerastase makes no such claim, and heavy styling creams built with silicones can leave gradual build-up with regular use.
4. Repairs bonds, not just coats them
No.9 runs on Olaplex's patented bond-building chemistry plus 48-hour pollution protection, working to rebuild damage rather than just style over it. Kerastase's cream smooths frizz and hydrates, but it isn't built around repair chemistry.
5. Yes it's a salon favorite. Skip it anyway.
Kerastase carries a real 4.6-star, 598-review track record and genuine salon credibility, that's not nothing. But it's priced and formulated for thick, heavily chemically damaged hair, and if that isn't your hair, you're paying salon markup for a job Olaplex already handles at a fifth of the cost.