The Remington Turkey Super Full tube is a .665 tube.Remington recomends a .675 tube for hevi-Shot but I shot 3 1/2 " #6 hevi-shot through it real well last year but 3" #5s shot just as well out of my wifes 870 using an undertaker .665 tube.
This year I will probably try the new Federal 3" with the flight control wad.They recommend a .665 to .675 tube

Bill