HUB Direct Thread Suppressor Adaptor - HYBRID UNIVERSAL BASE (HUB)- Mounts Suppressors Directly to Threaded Barrels - 1.375 X 24 HUB Mount Standard - Low Profile Flush Mounting - Available In 1/2 X 28 And 5/8 X 24 Thread Sizes - One-Piece Stainless Steel Construction - Black Nitride Finish