Tester is designed with you as the user in mind. Insert three AAA alkaline batteries, replace battery cover, remove plastic cap from probe tip, turn on using the Power Button (pointing toward the "SAM", wait 10 seconds to warm up, blue light will stop blinking when the tester is ready for use. Clean your loose gemstone prior to testing with clean tissue or jewelry cloth, grasp with tweezers and place onto the metal stone rest. Hold Stone Rest with one hand and the tester with the other hand. Probe tip must be placed at a right angle or perpendicular to the facet of the gemstone for an accurate reading. Mounted gemstones and small gemstones may be tested as well. Make sure to not touch the metal part of the jewelry piece with the probe tip during testing. Specifications Sheet Length 170mm/6.69 inches Width 31mm /1.2 inches Height 28mm/1.1 inches Weight (without batteries) 55g/1.94 oz Carat Size 0.01 to 10 carats