For hard plates, watch what they say in the description - There's a few different ways they can shape the plate: single curve, double curve, or flat. Double curve are more comfortable as a front plate, and single curve works just fine for a rear plate. You don't need a double curve plate in back, for comfort. Flat plates can dig into you when you're moving and static - depends on what kind of position you find youself in, or contort yourself into.