They're similar to MDMA - they're phenethylamines. 2C-B is about ten times as potent as MDMA, but they don't really have the same harsh after effects of the latter. They're also both significantly less empathogenic. 2C-I, I believe, lasts a long time. One review I read of 2C-B is that it's similar to the experiences of both MDMA and LSD while being not much like either, which while confusing, seems pretty accurate. 12mg of 2C-B at a concert is my favorite way to enjoy both. Do not insufflate it as it is not water-soluble. 2C-B also stacks nicely with MDMA.