Arctic Ice Tundra Series has been designed at the molecular level so that it freezes at an impressive -15º C (+5º F). What’s even more impressive is that its active ingredient maintains a consistent freezer temperature as it stubbornly thaws. Tundra Series 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.