5" x 1-1/4" Hard Rubber - Caster - Atlanta Caster & Equipment, Inc.
3" Extra Soft Rubber Caster Wheel - Caster City
6 Inches Heavy Duty Rubber Caster Wheels Anti-Skid Swivel Casters Wheels with 360 Degree for Set of 4 (2 with Brakes& 2 Without): Amazon.com: Industrial & Scientific