4 strong polyurethane wheels with stainless steel bearings Watertight, crushproof, and dustproof 2 level Pick N Pluck with convoluted lid foam 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