I am using test e 500mg ml and i can tell you that was a mistake. I'm getting used to it slowly, but man does this shit hurt lol. Ive used 300mg/ml before this, that hurt getting used to, and i was used to it by the time i started test 500. I'm not sure ill ever be able to inject it alone and not have a dead muscle unless i mix it with deca or equipoise. If you're a virgin to injections, stay away from that, it will not be fun. If I did that high of a concentration my first go at the needle, I might have thought I did something wrong and walked into a clinic to get checked out. Use 250, maybe 300 to start, maybe 400 after you get used to that. good luck, make sure your PCT is in order Dylan has a great video of it up on youtube.