For small pins. The PSA Custom Drop-In AR Single Stage Curved Bow Trigger is designed and engineered with the highest quality standards. Built-in a convenient drop-in design, even newcomers to the AR world can integrate this into their build for an easy and significant upgrade. You will feel a definitive difference over your old trigger with a lighter, crisp clean break and a short reset for more accurate shot placement. Upgrade your Mil-Spec factory AR-15 trigger now to experience the difference.