Carlson's Choke Tubes TruChoke 12 Gauge Improved Modified 72377. chokes and choke systems added to barrels use this Tru-Choke System. All small diameter 12 ga. chokes are available in stainless steel and may not be used with steel shot. This choke system is usually installed in barrels with outside diameters of .805 to .825 and is designed to be shot with 2 3/4" lead loads only. Specifications for Carlson's Choke Tubes Tru-Choke Flush Mount Replacement Stainless Choke Tubes: Manufacturer: Carlson's Choke Tubes Fabric/Material: 17-4 Stainless Steel Gauge: 12 Choke Tube System: Tru-Choke Quantity: 1 Additional Features: Non-Ported Features of Carlson's Choke Tubes Tru-Choke Flush Mount Replacement Stainless Choke Tubes Tru-Choke 12ga Flush Cylinder Package Contents: Carlson's Choke Tubes Tru-Choke Flush Mount Replacement Stainless Choke Tubes wrench Carlson's Choke Tubes 72377: TruChoke 12 Gauge Improved Modified