Four wheels on the outer edges/corners provide a natural, no-tip balance. Weight is distributed over the four wheel base for easy pulling with no back strain. The patented fiberglass frame is strong enough to hold an additional 100lbs. on top without losing balance. Exterior is made from durable nylon that is tear and puncture-resistant. Double zipper top opening provides easy access to contents. When not in use, remove the puller bar and fold to 3” for compact storage.This bag features an empty main interior compartment with straps for securing bulkier items such as art pads, canvas, small folding easels, sergers, sewing machines, etc. It also has two side pockets, two rear zippered smaller compartments, and a front panel (with storage pockets) that zips on three sides, allowing accessing to the main compartment from above or in front.