1 inch is usually what is preferred. if you have excess bodyfat or large delts, you will prob be ok. if you are skinny or lean, then 1inch would prob be better. you can make a 1inch with what you have. just cut the cap to where theres about 1/5th inch left and put it back over the needle and then you will have a 1inch syringe , homemade style. a bro on here taught me that but cant remember who.