I have a 535 which takes 3.5 inch load. Huntswith is right about the difference, also they are going to stop making the 500's because the only difference between a 500 and a 535 is that a 535 takes 3.5 inch load but 500's don't. So if your are buying, buy a 535 or the 835, why because I just bought it in the fall.
hope I helped
Buckshooter