This Presidium Gem Tester II identifies diamonds/moissanites and most colored, polished & unpolished gemstones. This Gem Tester II comes with a detachable probe pen with retractable thermoelectric probe tip that ensures constant pressure between the probe & gemstone. With consistent and reliable results every time, this Presidium Gem Tester II also features a metal alert buzzer to ensure that probe tip is in contact with the gemstone during testing. Not only does it have a clear and easy-to-read analog dial, but it can differentiate between 15 types of gemstones. Unit operates with 2 AA batteries or on an AC adapter (included). Comes with a protective convenient carrying case and is covered under a 1 year manufacturer's warranty.