The ELF AR-9 Drop-In Match Trigger has been built for performance and is secifically developed for 9mm and .45 PCC platforms. It has a u-shaped captured disconnector that forces a positive hold on the hammer and also has a "pad" that matches up to an extension on the hammer. The pad is directly in line with the rear trigger pin so when the hammer is stopped by those matching surfaces it effectively eliminates trigger slap from the hammer hitting the disconnector and greatly enhances the feel of the trigger during live fire. It utilizes an aerospace grade sealed bearings, making for an incredibly smooth and fast trigger pull. Pull weight is so easy to adjust it can be done in seconds without removing the trigger from your lower receiver. A second-to-none drop-in trigger system that is strong and light, made of wire EDM machined, hardened A2 tool steel and lightweight aircraftgrade aluminum. The AR-9 is compatible with the Sig MPX.