Rearden MFG 10087 R2S, 1/2x28 Threads, .40 Bore, Heat Treat Finish, Square Shoulder

Thread Pitch - 1/2x28Weight - 2.0 ozLength - 1.74"Length Added - 1.115"17-4 PHAtlas and Atlas XL compatiblePlan B compatibleH900 Wheat Finish (Variations exist)Shims not included, if you would like to specifically time this, shims will be required.Note: your barrel may require a shim if the manufacturer did not put a thread relief on it.These fit Plan B type mounts. Always use an alignment rod to ensure that the entire system is set up correctly. Make sure all surfaces are cleaned and the muzzle