AR-15 single stage trigger assembly with combat reliability and made with full strength music wire springs for fast lock time and reliable discharge with factory or military ammunition. The assembly is contained in a high grade 410 stainless steel housing. Factory tuned and set for 3.5 lb. or 4.5 lb. pull with minimum take-up and over-travel. Installation is fast and simple: simply insert the one piece assembly and install the supplied over sized pins. Designed to fit mil-spec receivers with small pins. Does not fit Colt AR-15 w/ sear block.