This leave-on AHA (and PHA, and BHA!) treatment is fantastic and fun. Not sure of the exact concentration of acids, but definitely more exfoliating than a 5% glycolic like Nip + Fab Glycolic Fix Extreme, Pixi Glow Tonic, etc. I use a tiny amount of this each night; it goes a long way! I also can take it to close to the lash line. I layer it in my routine as a last step before using a moisturizer on top. Will definitely buy again!