The ELF Drop-In Match Pro Trigger has been built for performance. The Elf Match Pro Trigger is identical to the Match Trigger with the addition of a proprietary threaded mounting system. The combination of aerospace grade sealed bearings, precision ground threaded bushings, and screws instead of traditional pins provide a rock-solid trigger system. Since their inception, AR platforms have always used pins to mount the trigger and hammer in the lower receiver. Because pins require some "play" in order to be installed, there is always a little play in the trigger system. This new threaded system adds a level of "solid" you need to feel to understand the difference. 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 AR- 15 drop-in trigger system that is strong and light, made of wire EDM machined, hardened A2 tool steel and lightweight aircraft-grade aluminum. Installation can be done in minutes using the supplied installation screws. The Match Pro trigger may be ordered with a curved or straight shoe. The amazingly short takeup, glass-rod crisp break and next to zero over-travel can be compared to the finest custom 1911 triggers. Adjustability puts you in charge based on your current use. If you are looking for the finest adjustable trigger for your AR-15 platform, this is the trigger system for you. Specifications for Elftmann Tactical Elf Match Pro Trigger with ELF PRO-LOCK Threaded Mounting System: Manufacturer: Elftmann Tactical Color: Black Trigger Shape: Straight Trigger Pull Weight: 2.75 - 4 lb Gun Model: AR-15 Gun Type: Rifle Condition: New Last Chance: Yes Features of Elftmann Tactical Elf Match Pro Trigger with ELF PRO-LOCK Threaded Mounting System Proprietary Threaded mounting system for rock solid installation. Compatible with ALL calibers - 5.56, 9mm, .308 etc. Fits any mil-spec AR-15 (Standard pin size, no large pin Colt) Absolutely Drop-Safe regardless of pull-weight Factory set Pull-weight is approximately 50% lighter than that of a standard AR-15 trigger, providing a great combination of speed and accuracy Adjustable from 4lbs to 2 3/4lbs without removing from lower Full power proprietary Double-Double torsion hammer spring ensures proper ignition of primer Very short pull and reset allows for rapid follow up shots and greater accuracy Sturdy trigger assembly designed for rugged, trouble-free use; Made of lightweight aircraft-grade aluminum and hardened steel Unique design of disconnect allows full 1/4 width eliminating possibility of wear and double-firing High performance trigger and hammer needle bearings for smoother and faster firing Benefits a wide variety of AR-15 enthusiasts, including collectors, competitive shooters, hunters, military, law enforcement, and disabled veterans Package Contents: Elftmann Tactical Elf Match Pro Trigger with ELF PRO-LOCK Threaded Mounting System What firearm models does the manufacturer say Elftmann Tactical Elf Match Pro Trigger with ELF PRO-LOCK Threaded Mounting System is compatible with? The manufacturer suggests that Elftmann Tactical Elf Match Pro Trigger with ELF PRO-LOCK Threaded Mounting System is compatible with AR-15