Fits Beretta shotguns with the "Optima Choke Plus" system (Xtrema-Xtrema 2 & most AL391 after 2003) Unique internal construction and .643 exit diameter. Designed by 4-time winner of the NWTF Still Target World Championship Shoot. This choke tube is rated for all shot types, (no steel) including Hevi-Shot and all tungsten-based shotshells. It delivers excellent, consistent patterns with a variety of shotshells. *The SSX set a World Record, that remains unbroken with the 2 oz. Hevi-13 Bronze" shotshells, by shooting the highest score ever recorded by the NWTF at a Sanctioned Still Target Shoot with that shell. This is the choke that Clark Bush used to win the World Championship Still Target Shoot in 2009.