"Universal Server Rack Casters | Bolt Pattern: 45mm x 75 mm | Hardware IncludedThis set of four M6 2-inch casters. while designed for StarTech.com racks. can be added to the bottom of any server equipment rack. network rack. A/V rack. etc. with a 45mm x 75mm bolt pattern. Ideal for replacing damaged casters or upgrading a standing rack to a rolling rack for additional mobility. RKCASTER2 is backed by a lifetime warranty and free technical support.StarTech.com Rack CompatibilityReplacement Casters For:Optional Casters For*:4POSTRACK12URK1224WALHM4POSTRACK25URK1232WALHMRK1233BKMRK1520WALHMRK1833BKMRK2620WALHMRK2433BKMRK616WALMRK2537BKMRK9WALMRK4242BK24RK4242BK30*Optional casters are sold separatelyThe StarTech.com Advantage- 2-INCH CASTER WHEELS: Four pack of universal swivel casters can be used as replacements on portable/mobile 4-post racks such as RK1833BKM. RK2433BKM. RK4242BK24 or to convert a floor rack to a rolling rack when casters are not included- TECHNICAL SPECIFICATIONS: Bolt