The Velocity Trigger for AR-15 rifles is a Single Stage Drop-In Trigger that provides a nice, clean & crisp trigger pull. The attractive price makes a quality AR-15 trigger achievable with any budget. Simple installation makes the process easy & quick. These feature a curved trigger. Recommend using: Anti-Walk Pins Part# 452-015-028 Not to be used with 9mm conversions or other recoil operated conversions. Mfg: Velocity Triggers