Maximum airline carry on size Watertight, crushproof, and dustproof Strong polyurethane wheels with stainless steel bearings Open cell core with solid wall design - strong, light weight Retractable extension trolley handle Easy open double-throw latches Stainless steel hardware and padlock protectors Automatic pressure equalization valve - balances interior pressure, keeps water out Comfortable rubber over-molded top and side handles O-ring seal