The Super ACR Trigger by Geissele is a two-stage, semi-auto only, drop-in replacement trigger. The S2S offers a clean and crisp 4-1/2 lb total trigger pull comprised of a 2-1/2 lb first stage followed by a 2 lb second stage. This trigger is constructed of precision investment cast steel and is machined on high-precision CNC equipment then through hardened for high strength and durability. All critical surfaces are machined on ultra-precise CNC EDM equipment to ensure consistently smooth trigger operation. All components are black phosphate coated to provide outstanding corrosion protection. A full-power hammer spring delivers plenty of energy for reliable ignition on all types of ammunition. Installation is easy and installation does not require any modification. The trigger kit comes complete with all parts, springs and installation instructions.