Petromax Cooler kx25/kx50 Powerless cooling system. The kx25 / kx50 are ultra passive cooling systems that provide a completely self-sufficient supply. The insulation layer of at least 45mm thickness allows the double-walled, robust body of the coolers to keep ice cool for up to 12 days. Powered by commercial ice, cold packs or dry ice, the boxes achieve a perpetually low temperature. Lid can be used as a seat. Lid guide for lashing straps during closed transport. Reinforced closing plate. Non-slip rubber feet. Ergonomic carrying handles.