Pantheon Arms AR-15 1.850-30 Thread Pitch Lock Collar Black Oxide. This unit is compatible with many Anderson Manufacturing Rock River Arms Unique ARs and YHM (and may work with handguards from other manufacturers as well as Pantheon Arms handguards). Threaded 1.850"-30TPI. Specifications for Pantheon Arms AR-15 Lock Collar: Manufacturer: Pantheon Arms Gun Model: AR-15 Color: Black Finish: Oxide Condition: New Package Contents: Pantheon Arms AR-15 Lock Collar Pantheon Arms DOLOSLC: AR-15 1.850-30 Thread Pitch Lock Collar Black Oxide