These Granite Cooling Stones are made from granite quarried from Scotland's Aisla Craig near the Mull of Kintyre which is the same granite used for most of the worlds curling stones because of its low quartz content and toughness on ice.

Simply keep the stones in your freezer so they are reay to pop into your drink. 

The granite is totally inert and non porous so will not affect the taste of your drink.