Zuca Sport Bag - Skulls with gift Lunchbox and Seat Cover Gift with Purchase Inspired by aerospace technology, the aluminum alloy frame is light, super strong and rated to safely support up to 300 lbs The removable, hand washable, Insert Bag is made from premium water resistant 600D polyester The dual wheel system climbs stairs and curbs with ease Magneto dynamic 4" polyurethane wheels absorb shock and make for a seriously silent ride