I have no clue what fits it since I have all Mossbergs. He has a Remington 1100 magnum, that takes 3in shells. He bought an aftermarket barrel for it, so it now has screw in chokes. He wants to shoot heavy 13s. I suggested a jellyhead .660, since that is what I got in my 500, and worked so well. So, can anyone tell me what fits it? Does anyone have something that will work well with H13 that they want to part with? Scott.