I didnt think you ever did injectables....3cc in one shoulder?!? hmmm. idk you must have some big shoulders lol.25G 1" for Shoulders and 25G 1.5" for Glutes.
Note : I have used 1.5" for Shoulders and injected up to 3cc/3ml.
So I would just order the 25g 1.5" so you can use them for anything. Multi-Purpose.
The 29g slin pins will be too small for the oil.