What syringe size / needle length should I use?

I've been taking BPC/TB for about a month now and noticed there's a lot remaining in the syringe / needle after injection using the 10mL syringes I bought. Should I be using a smaller 3mL or 5mL syringe? Currently taking 1 unit of BPC per day and 4 units of TB twice weekly. Any brand recommendations would be welcome as well.