Caster replacement depends on the style of cart. Below are different wheel bases to help you determine your cart style and the part number needed. 

A 5-wheel base with a blue stand and rollerblade-style casters requires Part Number CR0008H1A and a minimum purchase of (5) casters.

A 5-wheel base with dual black wheels or single grey ones now require the dual black version for replacement regardless of which style you have (Part Number RS-0008-08). These items can be purchased online at: https://store.gcx.com/products/rs-locking-twin-wheel-casters-4-10-2-cm-set-of-5.

A 4-wheel base comes in a variety of options. Therefore, we recommend taking a photo of the base/casters and sending your request to sales@gcx.com. In addition to the photos please include the make and model of the device the cart is holding.