Harper Trucks exclusive I-Beam Steel-Tough nylon truss is 30% lighter than steel and designed to be as strong as steel or aluminum hand trucks. Built-in stair glides for easy moving up or down stairs and curbs. 8" wheels with solid rubber tread and 3" swivel casters for easy maneuverability. Made in USA. Frame factory assembled - Requires easy assembly of wheels and base plate.

http://www.amazon.com/gp/product/B00EUUZAUG/ref=pe_62810_136460320_em_1p_0_ti

They also offer a larger model.

http://www.amazon.com/Harper-Trucks-PGDY...3186&sr=1-2

http://www.amazon.com/gp/product/B00D7HC024/ref=pe_62810_136460320_em_1p_5_ti

Regards

Jerryghr