The nurse who will be shooting me up uses retrackable needles. Once you use them a protective guard shoots out and covers the pin so u cant prick ur self accidently. She is a nurse and said there kidna expensive if u want them. What u do i only seen this once and i wasnt really payin attention but u connect the retracktable part to the needle and once ur doing injecting the guard pops out and covers the pin kinda cool just wanted to let u guys know about it if u already havent cause it will prevent u prickin urself and most imporatntly say u do it for a friend and u accidently prick ur self wit that needle u use on him.