Ruger 57 Threaded Barrel Kit. The factory- manufactured threaded alloy steel barrel accepts any 1/2''-28 (Class 2A) muzzle device. This kit contains a factory-manufactured alloy steel barrel for optimal fit and function. Installing the threaded barrel is quick and easy with no gunsmithing required. Thread protector adapter and wrench included. Specifications for Ruger 57 1/2-28in Threaded Barrel Kit: Manufacturer: Ruger Color: Gray Fabric/Material: Alloy Steel Threads per Inch: 1/2x28 Caliber: 5.7x28mm Gun Make: Ruger Gun Model: Ruger-57 Additional Features: Threaded Condition: New Package Contents: Ruger 57 Threaded Barrel Kit 1/2"-28 What firearm models does the manufacturer say Ruger 57 1/2-28in Threaded Barrel Kit is compatible with? The manufacturer suggests that Ruger 57 1/2-28in Threaded Barrel Kit is compatible with Ruger-57Ruger 90739: 57 Threaded Barrel Kit