Wagner Jam-Proof Ball Bearing Casters feature prongs that cover the axle that keeps thread from the caster wheel where it can't clog or jam the wheel movement. Thread collects on the caster frame. To dispose of the thread, one cut will suffice. Disassembling for cleaning is completely eliminated. Mounting type casters: Swivel and Rigid Plates are 2-3/4" x 3-3/4" with four (4) .343" holes on 1-3/4" and 3" centers. Stem type caster: Stem is 1" long with 3/8-16 thread.