Feature:This kit is used to verify the gold content in items! Apply a drop of this solution to a small sample of the item to be tested onto the test stone.then the real gold will stay on the touchstone, false one will be dissolved or oxidized to blueIf the sample disappears, then the item is below the karat of the solution This solution works for testing any gold which you believe to be 10K, 14K, 18K, 22-24K, Silver, and Platinum pure. Acid changes color based on purity. Very easy to use, Ideal for testing jewelry, coins, antique gold, silver, platinum collectibles, and more! Warmly Tips:If u want test your gold ring is real or not, just need rub black stone, and leave a small sample on stone,Apply a drop acid test on stone. real gold will tay on the touchstone, false one will be dissolved. Specifications:Type: A/B/C(Optional)Material: High purity Graphite Stone & Acid Testing Water,Size: Stone: Acid Testing Water :4.5 X 3 cm/1.8"X 1.2" ( 3 ML)Graphite Stone :8 X 5.5 cm/3"X 2"Quantity: 1 set / 1 Pc, Note:Size for manual measurement, there may be a 0 to 2 cm error, belongs to the normal phenomenon.And due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package includes:1 PC X Acid Testing Water,( 3 ML)or 1 PC X Graphite Stone. or 1 Set X Acid Testing Water & Graphite Stone.