Strengthening broken strands every time wash day rolls around, Olaplex No. 4 Shampoo is the go-to for anyone with damaged, bleached or stressed-out locks. Beyond its major moisturising skills, what really sets this vegan shampoo apart is its ability to repair and maintain bonds in the hair and decrease the chances of breakage and split ends. Use it after the No. 3 Hair Perfector Treatment to part ways with frizz for good.