30 and Volume developers are all in the same, however, I favour this brand a little bit more 'cause there is some conditioners already built in which is appreciated. It is nice and thick which is awesome for my hair since I have a lot of layers. It also ensures that I have a little more of an even bleach application. It is compatible with most bleach powders. The thing that sucks is that it comes in a 4 oz bottle for $3.99, however, it would be appreciated if they had a larger bottle, especially for people like myself who frequently bleach and dye their hair weird colors. Unlike other developers this has a very mild smell. read more