This choke will fit Benelli shotguns with the "Crio-Choke" system, SBEII, M-2, Vinci, Super Vinci, etc. (It will also fit guns with the "Mobil" choke system but will protrude from the muzzle an extra inch.) 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.