4 strong polyurethane wheels with stainless steel bearings; 2 level Pick N Pluck with convoluted lid foam; Watertight, crushproof, and dustproof; Open cell core with solid wall design - strong, light weight; Retractable extension trolley handle; Fold down handles; Easy open double-throw latches; Stainless steel hardware and padlock protectors; Automatic pressure equalization valve - balances interior pressure, keeps water out; O-ring seal