I agree. This is a personal preference. If your really concerned about needle pain, slin needles probably will be the best to choose.as these I don't feel anything when they go in ( hcg, M2, hgh injections). if your not concerned with a little injection pain and pip then you can use various gauges of needles. I use between 23g - 25g and mostly I do not get any injection pain as long as I go straight in .don't hit anything where I am injecting ( a nerve etc). I do thighs mostly cause I can sit down and relax my legs and they are easy to get at as they are in front of me.. Length I use is 1 inch down to 5/8's. Most of my workouts cause me significant more discomfort than pinning, so mentally it's not a big deal. I have done glutes as the needle goes in like a hot knife through butter, however I have a hard time reaching that location so I don't do it anymore.