I have been using 27 gauge .5" insulin syringes and rotating between quads and shoulders. Didn't want to have to inject myself with large needles twice per week for the rest of my life. Using a smaller needle and rotating between 4 injection sites is really nice, don't have to worry about scar tissue. The .5" needle won't penetrate deep into the muscle like a 1.5", but it gets deep enough. I learned this technique from some guys on this forum that are very experienced with TRT. Check out a previous thread of mine called "test cyp IM with insulin syringe." It's on about page 5 of previous threads, but there is some good input on that thread.