Thread Pitch - M18x1.5 Weight - 1.96 oz Length - 2.25" Length Added - 1.305" 17-4 PH H900 Atlas and Atlas XL Compatible Plan B Compatible PVD Finish Shims not included Tapered for barrel Designed for 8.6 Blackout These fit the 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 device has been torqued and Rockset to the barrel. Use on a Q can voids your warranty, be warned. Torque the muzzle device to approximately 30 ft lbs. Make sure the muzzle device is square against the shoulder. When setting the silencer on the muzzle device, ensure that the threads and tapers are clean. Torque the suppressor to 10 ft lbs. Ensure alignment. Enjoy.