Franklin Armory F17-X .17 WSM 20in Upper Kit w/ 10 Round Rifle Magazine 1-9 Twist 1/2x28 Aura Black. Chambered in the amazing .17 Winchester Super Magnum this piston driven upper receiver provides a cleaner and flatter shooting solution for all kinds of pest control. The F17-X R2 has a new Osprey Defense slim piston system. The new piston system automatically adjusts for suppressed or unsuppressed use no adjustments needed This pairs perfect for use with the 16'' barrel which is threaded in the common 1/2-28 thread pitch perfect for use with compatible suppressors. The new proprietary handguard features an integrated barrier stop / indexing point and is M-Lok compatible. Specifications for Franklin Armory F17-X .17 WSM 16in Upper Kit w/ 10 Round Rifle Magazine: Manufacturer: Franklin Armory Color: Black Barrel Length: 20 in Magazine Capacity: 10 Round Caliber: .17 Winchester Super Magnum Barrel Twist Rate: 1-9 Threads per Inch: 1/2x28 Gun Model: Franklin Armory F17-X Muzzle Device: Aura Muzzle Brake Quantity: 1 Gun Rail: Picatinny Magazine Included: Yes Package Contents: Franklin Armory F17-X .17 WSM 16in Upper Kit w/ 10 Round Rifle Magazine What firearm models does the manufacturer say Franklin Armory F17-X .17 WSM 16in Upper Kit w/ 10 Round Rifle Magazine is compatible with? The manufacturer says that Franklin Armory F17-X .17 WSM 16in Upper Kit w/ 10 Round Rifle Magazine is compatible with Franklin Armory F17-XFranklin Armory 00-40075-BLK-10RD: F17-X .17 WSM 20in Upper Kit w/ 10 Round Rifle Magazine 1-9 Twist 1/2x28 Aura Black