Gio,
I use the one inch pins for the glutes and never inch and a half.
As for the delts, I never personally inject there just because I am
afraid of hitting a nerve or the bone or something. However, others
say that one inch is what you should be using on the delts. Once again
because I am afraid to do my delts myself, I look at my delts and wonder
where in the world that entire inch is going to go to. But when you go to
the doctor that is what you see him use. Anyways, to really answer your
question, an inch in the glutes is good enough even though a inch and a half is preferred. An inch into the delts is what you are supposed to do.