The high-accuracy diamond tester pen has advanced thermal conductivity; this tester accurately distinguishes real diamonds from common like crystal or cubic zirconia. Ideal for home use, collectors, or resellers. Diamond tester professional features a built-in UV light to reveal diamond fluorescence-an important clue in verifying authenticity. Different materials show different reactions under UV, making this feature useful for assessment After a 25-second warm-up, hold the conductive panel on the top with your finger, tip the vertical diamond 90 degrees: a red LED flashes and a buzzer sounds when a real diamond is detected Use with bare hands (avoid gloves), Best results at room temperature (10-35). Accurate for diamonds 0.02 carats and larger. Diamond tester pen compact size with protective case makes it easy to keep in your bag or drawer, leather pouch keeps your tester safe- perfect for on-the-spot diamond checks , in stores, or while traveling. Color:As Shown Material:Metal+Plastic Package Contents: 1 * diamond tester pen 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.