The unique wheels permit easy rolling of heavy loads over most terrains including soft sand, dirt, mud, snow, or environmentally sensitive areas.The wheels are very tough, pliable tire for easy rolling even over bumps, stairs, or curbs. The 30cm wheel has a maximum weight limit of 121 lbs. per wheel. It will get you over terrains that are not accessible to other wheels. The 30cm wheel is also available in rigid and swivel caster wheels.