EXTENDED CHOKE WITH DIAGONALLY-PORTED DESIGN FOR RECOIL REDUCTION. CONICAL/PARALLEL INTERNAL CONFIGURATION.
EASY TO INSTALL AND REMOVE WITH YOUR FINGERS. NO SPECIAL WRENCH OR TOOL REQUIRED. 
FITS BARRELS WITH OPTIMA HP STYLE THREADS.
BERETTA HAS MULTIPLE THREAD SYSTEMS THAT ARE VERY SIMILAR TO ONE ANOTHER BUT NOT INTERCHANGEABLE. 

OVERALL LENGTH: 4 9/32"
PORTED SECTION LENGTH: 1 17/32"
IN-BARREL LENGTH: 2 1/16"
STANDARD BORE SIZE: .733"
MATERIAL: 17 - 4 STAINLESS STEEL