10PK Ball Bearings, 13mm Each - Steel - Great for Physics & Mechanics Experiments - Eisco Labs: Amazon.com: Industrial & Scientific
XiKe 8 Pack 1" Roller Ball Transfer Bearings, Hard Chrome Steel Ball Transfer Unit with Swivel Ball Caster Rollers, Used for Roller Stand, Conveyors,Transfer Equipment and Transmission System: Amazon.com: Industrial & Scientific
SKF 7308 BECBJ Angular Contact Ball Bearing, Single Row Explorer, 40 mm Bore, 90 mm OD, Steel Cage: Amazon.com: Industrial & Scientific