This is a very versatile product. I don't use it as directed, so my review is based on how I use it. I mix about 1/4 of the bottle with Queen Helene Cholesterol Conditioner and apply it as a weekly hair treatment. My hair is really damaged and doesn't hold color well. By mixing this semi-permanent color with my deep conditioner I am able to brighten/darken my hair color without damaging it. It definitely makes a difference. I can't imagine using it all over my hair though. It's such a small bottle that I'd probably need 3 to cover my whole head with it full strength. It is also very watery, which is fine when I mix it with the conditioner that is thick. Trying to apply it as is would probably be really messy. I can tell that it would definitely make my hair darker if I used it full strength, considering it darkens my color when diluted.

This can be purchased at most beauty supply stores, such as Sally Beauty, and on Amazon.com for about $6.