CMC Triggers AR-15 Threaded Stripped Upper Receiver Mil-Spec Black Small. Forging packs the grain structure tighter than billet which is why it's still the go-to for hard-use guns. It's machined to M16/M4 military standards so your barrel handguard and bolt carrier all drop in where they should. M4 feed ramps help rounds run up smoothly from the magazine. The top rail is MIL-STD-1913 Picatinny ready for your optic or backup sights. Ships stripped so you can build it out however you like. Specifications for CMC Triggers AR-15 Threaded Stripped Upper Receiver: Manufacturer: CMC Triggers Fabric/Material: 7075-T6 Aluminum Caliber: 5.56x45mm NATO Gun Make: AR Platform Gun Model: AR-15 Package Contents: CMC Triggers AR-15 Threaded Stripped Upper Receiver What firearm models does the manufacturer say CMC Triggers AR-15 Threaded Stripped Upper Receiver is compatible with? The manufacturer says that CMC Triggers AR-15 Threaded Stripped Upper Receiver is compatible with AR-15CMC Triggers CMC-AR15-UR-STRIP: AR-15 Threaded Stripped Upper Receiver Mil-Spec Black Small