Well, I draw my juice out with one needle and then I change the pin before injecting, Why? when you are drawing your tren, test and or eq out, you are putting the pin through 2 or 3 rubber stoppers, that will doll out the needle head believe it or not, so when you stick it into your skin it is not as sharp, that's why it's better to change it, also less scar tissue in the long run.
