CasterHQ's Mold-on-Rubber caster wheels have soft rubber tires molded onto iron centers. Soft rubber provides more desirable operating characteristics than any other wheel material. It is quiet, absorbs shock (prolonging equipment life and protecting cargo), can roll over small objects, protects costly floor surfaces, and minimizes vibration. The Conventional Moldon rubber caster wheel falls short of perfection in its limitation under load - it does not roll easily. Load capacity ratings do not take into account the effort required to manually move a load (drawbar pull measured in pounds). If cargo is to be moved manually on Conventional Moldon rubber caster wheels, reduce capacity ratings by 50% and select the largest practical wheel diameter. These caster wheels should not be left standing under load for extended periods as the tires may take a permanent "set" or develop flat spots. They can be used on almost any dry factory floor. The bonding agent which holds the rubber tire to its iron center can be affected by exposure to some chemicals, impact, overloading, and the buildup of heat. Tire hardness is 65 to 75 Durometer, Shore A. Temperature range is -20° to 159° F. Features Rubber tread vulcanized to heavy duty cast iron core. Offers shock absorbing semi-cushioned ride, rolls easily over small debris, rough floors, cracks, floor joints, etc. Provides good floor protection and quiet rolling operation. Economically priced cushion wheel. Works well in outdoor environments; however cast iron core can rust; if this is an issue look at using aluminum or plastic core wheels. Black rubber tread can mark Durometer: 80 Shore A (+/-5). Temperature range: -40° F to 180° F.