Well, I always use different pins to draw with than pin with so maybe I didn't screw the needle on good enough..when I went to hit my quad I aspirated and I didn't even see an air bubble..pushed it in and seemed like it leaked out of the plunger..some must have leaked from the tip too cuz it was on my hand and my leg..alin a retractable pin u pushed it in and when u get down to the end it pushes the oil in and then the needle retracts into itself