1 inch
23 or 25 gauge depending on how thick the oil i am using is..

I am a slow poker by the way, i line it up and push in the needle slowly

My left bicep has a lot of nerves for some reason
(seems like much more then my right?)
So when i go in, if i feel a twitch i just realign a little bit and all is good

I would suggest using less agressive oils like
test e 250 / Deca / EQ

I did test prop a couple of times and the pain was too annoying all day long

Had some really great Canadian Vet Winny, stuff was super smooth
i could inject that stuff anywhere without any pain.