Wilson Combat TRTTUMIL Tactical Single Stage Trigger is a modular trigger unit that can be easily installed in any AR pattern lower in under a minute without tools or removing the selector. It delivers a crisp 5-5-3/4 lb pull and is a self-contained trigger module. Hammer, trigger, and disconnector are made from H13 steel and heat treated for wear resistance. Compatible with standard GI trigger pins (.154 diameter) in AR lowers of various calibers, but not compatible with Colt rifles with pinned sear blocks or Bushmaster ACR. MR556 and ARs with firing-pin safety in the bolt carrier require TTU-3G or TTU-M2. Not recommended for .22 LR conversions. Not shipable to California, Illinois, or Washington.