This product in display is Gold Testing Stone. Overall length/dimensions: 3 x 2 x ½ inch - Thickness. This is a acid test stone. This black testing stone for test 9ct1 14-15ct1 18-24ct, Gold, Platinum, Silver, Test Karat Value Purity Jewelry Scrap Precious Metal. Use this stone with acid solutions to test your item. Simply rub test subject onto stone and apply testing solution directly onto the stone.PLEASE CLEAN AND APPLY OIL BEFORE USE. Note: Remember to wear eye protection. Note: Photographs are for illustration purpose only. Actual item may slightly differ from the pictures shown.Scorpion is committed to providing the customer with the best source for value possible on the market. You will enjoy the quality, function and usefulness of our products.