Going from dark brunette to blonde can be quite an endeavor—and it can also be really tough on hair. Bleaching damages the bonds in your hair, which can leave it brittle, dry, and mangled with split ends. It’s important to try and tackle that damage before it even starts if you’re considering going lighter, which is why MacPherson turned to a product that’s already gone viral on TikTok: K18’s Leave-In Molecular Repair Hair Mask.

The K18 Leave-In Molecular Repair Hair Mask is basically a hair mask that you don’t wash off, and it’s clinically proven to start reducing hair damage in just 4 minutes. It’s ideal for someone like James who just bleached their hair, but it’s also a miracle-worker for anyone who has damage from chemical services or heat.