I have done Bk-MDMA once on accident and it was garbage. Actually garbage is an understatement to compare it to Mdma, I felt absolutely no euphoria, talkativeness etc or any positive effects what so ever. Colors seemed SLIGHTLY brighter but that could of been a placebo honestly, it was just so annoying when your in the middle of rolling and not like a stimulated feeling kind of but no actual high I guess? & it lasted like 2 hours before I just went to sleep. Maybe I didn't do enough but it was horrible for me, never again I'll tell you that.