The Geissele SSA trigger installs in your lower receiver in the same way that a Mil-Spec trigger is installed and uses a standard .154” trigger and hammer pin so it will fit in any Mil-Spec stripped lower receiver. It features a curved trigger bow that feels comfortable on your finger and helps give you a consistent pull every time. Not only does it work in 5.56 or .223 AR-15 rifles, but it works in .308 AR-10 pattern rifles. Each trigger is precision EDM wire cut from heavy duty tool steel with a durable black finish giving you the reliability and durability you can depend on.