Our individually-sold, non-marking rubber threaded casters accommodate existing mobile wire shelving with a damaged wheel, as well as solutions without four posts. They are compatible with Shelving Inc. brand posts only. If you have another brand, please use these stem casters. Sold individually, available in 4-pack here Ideal for transit over rough surfaces Bolt with 12 threads per inch screws into bottom of Shelving Inc. brand 1"dia post Absorbs bumps and shocks Swivels 360 degrees for easy steering Step-lock brake controls movement Non-marking, won't scuff floors For stability, not recommended for use with 8"d wire shelving Shipping: Next Business Day