depends how much of a fat-ass you are...literally, lol. If you're around 13%bf or below, you can get away 1". But if you're a fat-body, 16%bf plus, then you probably need to get 1.5".
damn - sometimes i'll even use a 5/8" with no problems or doubts that it is getting i.m. (...i guess that makes me a skinny-ass??...actually, i just don't have an ass)
Another way to tell is if you flex your ass checks and you visibly see where the muscle is and can touch it then inject there. But don't inject when your flexed...unflex and then stick there.
if you have low fat % it is fine, if you have more fat, then you would want to use a 1.5 to ensure hitting the muscle and not injecting into the skin layers which can cause severe skin infection
depends how much of a fat-ass you are...literally, lol. If you're around 13%bf or below, you can get away 1". But if you're a fat-body, 16%bf plus, then you probably need to get 1.5".