With Wilson Combat's advanced engineering and design the TTU 3G trigger offers an impressive pull of between 3.25-4 lbs. without any need for alteration or tweaking.This reliable and sturdy trigger can be relied upon to provide reliability when you need it most!It also has a reduced reset for rapid follow up shots and its unique hammer geometry ensures reliable firing with all types of military/surplus ammo and it meets or exceeds drop safety standards due to its 1911-style half-cock notch. Constructed with H13 heat-treated trigger hammer sear and a stainless steel spring for straightforward installment our pre-assembled CNC machined housing will ensure bulletproof reliability.Developed by shooters for shooters after rigorous tests the Tactical Trigger Unit has firmly established itself as one of the best drop-in AR triggers available on the market today.Compatibility Notes:Colt brand rifles made for commercial use between 1991 and 2009 will generally have a proprietary trigger pin size of .169" and are not compatible with any Wilson TTUColt rifles produced with pinned-in sear blocks are not compatible with any Wilson TTUWilson Combat TTU is not compatible with the Bushmaster ACRThe MR556 and any other AR style rifle with a firing pin safety mechanism in the bolt carrier is only compatible with the TTU 3G (TR-TTU-3G)or Two Stage Models (TR-TTU-M2)With .22 LR AR conversions or complete .22LR caliber AR-pattern rifles it is recommended that the standard single stage TTU (TR-TTU) or two stage TTU (TR-TTU-M2) trigger be used along with high or hyper-velocity ammunition for best reliabilityThe TTU is compatible with the S&W MP-10 .308 AR but the rifle's ambidextrous bolt catch must first be removed to install the trigger unitBecause of the short fast reset of the TTU always use a firm grip and solid hold when shooting from the bench or prone to ensure that bump firing does not occur.