The Avanti® Ice Brick is an eco-friendly alternative to conventional plastic 'gel' ice packs. Perfect for school, work, camping, and other outdoor activities, the sender design allows easy stacking in the freezer and takes less space in your lunch box or insulated bag. Crafted from high quality food grade 304 stainless steel, it is filled with distilled water that is hermetically sealed allowing the Ice Brick to remain frozen longer and stay cold for hours, keeping lunches cool and fresh. Just store in the freezer for a minimum of 4 hours or overnight to freeze solid. Note: condensation is normal as ice thaws so please be sure to fully dry your lunch bag after use to prevent any bacteria build up in your preferred lunch bag.