Accurate Gold Purity Testing - Specially designed acids test kit for verifying the gold content in jewelry, coines, bullion, antiques, and collectibles. Easy-to-Read Color Change - Acids changes color based on metal purity, providing quick and reliable results. Multi-Metal Application - Ideal for testing 10K, 14K, 18K, 22K-24K gold, as well as silver and other precious metals. Simple Testing Process - Apply a drop of acids on the touchstone; real gold remains on the stone, while fake metals dissolve or turn blue. Essential Tool for Jewelers & Collectors - Compact, portable, and easy to use at home, in workshops, or on-the-go appraisals. Specifications: Optional Type: Common, Superior (Small) Size: Superior (Small): Length: Approx. 6cm / 2.4in, Width: Approx. 3.4cm / 1.3in Common: Length: Approx. 4.5cm / 1.8in, Width: Approx. 3.9cm / 1.5in 1 x Touchstone (Acids Testing Water Not Included) Color: As Shown Material: Natural Siliceous Rock Package Contents: 1*pcs gold testing kit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.