even if you're pretty lean you should go with a 1.5 for glutes, you'd be surprised how much there is between the skin and the muscle tissue there!! and also it's a deep IM injection you want it to be good in the muscle for your injections!! I use a 1 inch needle for everything else though... including traps, pecs, quads which is really all I shoot, four muscle groups... 8 basic sites... plenty to keep me on a good rotation!!