Amazing product!! The 512 removes all warm tones and brings back the even dark brown color! Now I can extend the periods between colorings. I also feel it takes away some of the gray in the roots. Let it sit for at least 15 minutes. I couldn’t recommend anything stronger if you have brown to dark brown hair that tends to warm tones you want to get rid of. Nothing but a gamechanger! The fact that it also nourishes instead of damaging the hair like silver shampoos and other crap that doesn’t work anyway is incredible!