The Harris Bipod Mounting Adapter #4 is a Universal Bipod Adapter that requires 2 inches of uncluttered barrel for mounting. It Fits barrels from .550 diameter (AR-15) to .800 (TC Super-14). Best application is on single shot pistols. Requires 6" or longer barrel to fold - Not recommended for shoulder guns. Note: Mounting bipods on barrels may affect accuracy.