TIENO 8 Reusable Diamond-shape Whiskey Stones Stainless Steel Ice Cubes Wine Chillers Gift Set with Freezing Storage Tray and Tongs FDA approval (we can provide inspection certificates if you ask): these sipping stones are made of food grade non-porous stainless steel filled with a secret, non-toxic liquid that has a lower freezing temperature than ice to enhance chill time. FUNCTION: Steel Ice proved to be the best of the bunch If you are looking for a way to keep your scotch or drink a bit colder without affecting the taste and flavor as ice melts and waters it down. REUSABLE : put the stainless steel whisky stones into refrigerator cooling 2-3 hours, then take out to use. Rinse with water and air dry after use. Suggested usage is 1 whiskey stone per 1 oz of whiskey you pour. PERFECT GIFT: Great for Whiskey, Scotch, Tequila or Bourbon Lovers and spirit drinkers. Coolest stuff for your beloved friends. ATTENTIONPut them into the glass gently although their Edges and corners are round design to avoid scratching your glass.BE CAREFUL not to chip your teeth or swallow the stone carelessly.