Arctic Ice Tundra Series Ice Substitute - Arctic Ice Tundra Series has been designed at the molecular level so that it freezes at an impressive 5 degrees F. What's even more impressive is that its active ingredient maintains a consistent freezer temperature as it stubbornly thaws. Tundra Series Arctic Ice is a portable, safe, and re-usable alternative ideally suited to replace dry ice. Arctic Ice Tundra Series works best when frozen for 36 hours at the lowest setting available on consumer freezers. (What takes longer to thaw, takes longer to freeze.) The purple interior turns white when fully charged. For extended storage periods, the cooler should be packed full of frozen goods and rarely opened. Arctic Ice Tundra Series is available in 4 convenient sizesSmall: Perfect for chilling insulated lunch boxes and mini coolersMedium: Just right for chilling small or mid sized coolers and insulated tote bagsLarge: Cover the bottom and cargo of your full sized ice chest with two or more of these large packs to keep it all cold, all daExtra Large: Cover the bottom and cargo of your full or Marine sized ice chest with these to keep it all cool, all day long