I DON' T KNOW THE CHOKE DIAMATER OF MY TUBE BUT CAME FROM WAL-MART AND IS CALLED STARDOT.I SHOOT THE 31/2" X #4 HEVISHOT AND IT IS AWESOME PAST 50 YDS.IN MY 870 EXP SUPER MAG.I AM NOT CONCERNED ABOUT DAMAGE TO THE CHOKE OR BARREL SINCE I DON' T SHOOT IT BUT 3 TIMES A YEAR.