Water Heater Insulation Kit 

Pro tip: This does nothing for convection or conduction heat loss. Instead, wrap the tank with standard R-13 fiberglass batting....THEN wrap with the radiant barrier (mylar bubble wrap). Also, you'll want to set the tank on a stand a few feet off the floor so you can insulate the underside and install a drain pan. Perhaps one day someone will manufacture a vacuum insulated tank eliminating the need for all this after market insulation in the first place 🤔.