This is the Piercision Rifles 9/16x24 Brake with a .880" OD. This is a great streamlined brake for the sporter and varmint contours barrels. The ports on it are all 90 degrees which redirects the gas blast/concussion away from the shooter. Very effective brake for its size.
The O.D. is .885 and can be turned down to .860.
Minimum Muzzle diameter for this brake is .620.