The 24K gold leaf Cube Glass is Nate Cotterman's signature, patented barware. A solid glass cube is fused to the bottom of the handblown glass. These can be stored in your freezer for a minimum 20 mins before use. (The glasses may live in the freezer until use as well!) The fused cube will get frozen and chill your room temperature liquid for about 20 mins! The gold leaf cube glasses are NOT dishwasher safe. Do not pour hot liquid into a cold glass.