CARLSONS WIN 20GA FLUSH IMPROVED CYLINDER Winchester, Browning Inv, Moss 500 Flush Mount Replacement Stainless Choke Tubes Made from 17-4 heat treated stainless steel, these chokes are for the Winchester, Mossberg 500, Browning invector, Weatherby, and Savage 12 gauge & 20 gauge shotguns. Steel, Lead, & Hevi-Shot may be used in all constrictions with the exceptions listed below. No Steel shot larger than #BB or speeds exceeding 1550 fps should be used in choke tubes tighter than full. No Steel Shot Larger than #4 may be used in our Turkey Choke Tubes These choke tubes are backed by Carlson's Lifetime Warranty and Made in the USA! Const.: Improved Cylinder Dia.: .610