The Wilson Combat TRTTUH2 or simply referred to as TTU, is a cutting-edge, single-stage trigger unit that you can conveniently install in any AR pattern rifle within a minute. Its effective design by Wilson Combat promises a robust, 4lb, ultra-sharp trigger pull, with no need for meticulous tuning or adjustments. The TTU assures a reduced, positive trigger reset for a swift follow-up shot on targets.This product\'s unique hammer design increases dependable ignition with various types of military and surplus ammunition. It also includes a 1911 style half-cock notch, allowing the TTU to either meet or surpass military standards for drop safety. The TTU comes in a pre-assembled, CNC-machined trigger housing including H13 heat-treated trigger, hammer, sear, and a resilient stainless-steel spring for a hassle-free installation process.Designed with precision and rigorously tested, the Tactical Trigger Unit has set a new standard for drop-in AR triggers. Wilson Combat AR-15 Tactical Trigger Units will function reliably in all standard USgi style AR-style lower receivers with regular GI trigger pins of .154\" diameter - this applies to all calibers including 7.62/.308 length AR receivers. Meanwhile, they are not compatible with Colt brand rifles produced for commercial use between 1991 and 2009 as these usually have a proprietary trigger pin size of .169\