The A461-4×1-1/2 caster is part of the Faultless 400 series designed for medium duty loads.  It has a 4-inch polyolefin wheel with a roller bearing and is ideal for tool boxes, bakery racks, and stock and hotel hand trucks.  The optional A plate is a bigger plate with a wider bolt hold pattern that distributes the weight of the load over a wider surface area.  This minimizes the load weight that is pressing directly down on the wheel and eases wheel movement with heavier loads.