RCBS Full Length Die Set For 300 Winchester Short Mag is a 2 die set. 2 die sets are used for Handgun and Rifle casings that have a bottle neck shape to them. This 2 set die contains a full length sizer die with an expander decapping unit. There is also a seater die with a bullet seater plug. These 2 die sets are different from 3 die sets in that 3 die sets are for straight wall handgun and rifle casings. The three die set also has a bullet seating die, expander die, and a resizing die with decapping unit.