I just used the clairol nice and easy dark brown think its #120. I pinned the system on a styro head and just combed the mixture t hru all of the hair the best i could. The ends were tough. My hair system is only once inch long. I think i left it on 10 mins. and rinsed it. I think its slightly too dark, but once i attached it and styled it, its not too bad. I have no idea what kind of developer they use. it was two bottles that i mixed together.