Company calls this a caster
A circular item made of metallic or nonmetallic material designed for use as part of a caster, rigid and/or caster, swivel. The tread may or may not be removeable and it is usually furnished with bearings installed. For items constructed entirely of one material see wheel(1), solid, metallic or wheel(1), solid, nonmetallic.
Classification: Hooks, eyes and eyelets, of base metal
NSN 6685-00-150-7080
NSN 5996-01-202-9338
NSN 5855-01-510-9416
NSN 6610-01-255-4544
NSN 6135-01-216-7170
NSN 5985-01-327-7578
NSN 6650-01-029-2995
NSN 5930-01-265-3969
NSN 5985-00-231-2810
NSN 5910-01-536-9965
NSN 5975-01-035-1141
NSN 5935-01-474-5571