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; Lifetime Guarantee of Excellence