Nexel Polyurethane Wheel Rigid Casters ● IMPORTANT: Rigid Stem Casters require the use of a tie bar to assure rigid caster alignment. For every two casters ordered, one tie bar must be used. The bar size must match shelf width ● Add these high quality casters to your unit and make it a mobile unit ● 1200 lb. capacity per set ● Includes four 5" diameter polyurethane wheel rigid casters and 4 protective bumpers ● Color: Gray ● Nexel's casters can be attached to any of its Shelving Units ● Limited 1 Year Warranty ● Nexel offers a wide range of shelving units and parts in many different finishes and sizes. Also offers several accessories (ledges, hooks, dividers, baskets, etc.), which can be purchased separately and extend the usefulness of your shelving unit ● Photos may not reflect advertised size.