Steer clear of fentanyl. My best friend in Detroit died from it (sold to him as heroin) and he isn't the only person in Detroit I know who died because of it. (Nobody asked to score or buy fentanyl - they wanted heroin - but got fentanyl instead.)

I can't comment on other cities - I wouldn't know. It varies from place to place. Speed is popular in LA, but nowhere to be found in Detroit.

The high from fentanyl is said to be similar to heroin, but much more risky in terms of an overdose. Sad shit. Stick to beer and whisky.