The three most common syringe types are Slip-Tip, Luer-Lok and eccentric tips, according to the University of North Carolina's Eshelman School of Pharmacy. The needles on the syringe vary primarily based on their thickness.
Slip-Tip syringe tips rely solely on friction to keep the needle in place, which is typically sufficient if the needle is attached correctly and there isn't too much pressure in the syringe, states the Eshelman School of Pharmacy. Luer-Lok syringes use a collar with grooves to secure the needle. Eccentric syringe tips position the needle off center and are designed for cases when the syringe needs to be parallel to the injection site.