Duck House NFL unisex Crystal Freezer Monster Mugs Officially Licensed By The NFL 38oz mug combines state of the art refreezability with team colors and graphics. Eliminates the need for ice as the technology keeps drinks "crushed ice" cold for hours without the watered down affect of ice. Place in freezer one hour or more prior to use, when frozen crystals will turn a frosty white color. Filled with non toxic, refreezable crystals.