Rearden MFG Atlas Alpha Heat Treat Suppressor Adapter 1.125x28. 125-28 like the Rugged Obsidian 9 and Obsidian 45. Rearden MFG does not recommend this on suppressors that use the low profile style adapters like the Omega 9k. Specifications for Rearden MFG Atlas Alpha Heat Treat Suppressor Adapter: Manufacturer: Rearden MFG Finish: Heat Treat Threads per Inch: 1.125x28 Length: 0.35 in Weight: 1.22 oz Features of Rearden MFG Atlas Alpha Heat Treat Suppressor Adapter Compatible with short Rearden devices (FHD Mini SPB RPB R2S) Compatible with Q Cherry Bomb and Other Plan B Compatible Muzzle Devices Package Contents: Rearden MFG Atlas Alpha Heat Treat Suppressor Adapter Rearden MFG 10097: Atlas Alpha Heat Treat Suppressor Adapter 1.125x28