True Fabrications Glacier Rocks Whiskey Soapstone Ice Cube and Rocking Tumbler 8 Piece Gift Set Glass tumbler construction and soapstone cube construction Set includes six cubes and two rocking whiskey tumblers Cubes will not scratch your glass, alter the flavor of your drink, or water down your drink Glasses are designed to rock back and forth, which actually helps to chill your beverage with gentle motion Freeze the cubes two hours in advance and use three cubes per glass for best results