Easy to use. LED light and audio result indication. The red light will be shown and the audio indicator will emit beeping sound if the stone is a real diamond. Metal alert for continuous buzzing sound when user accidentally touches metal rather than stone. If the stone is diamond simulated one, no beeping sound or red lights on. Simple calibration for stones of various sizes. With a testing platform for loose stones. Lightweight and easy to carry. Instantly distinguishes diamond from CZ and common simulants (excluding moissanite) Distinctive audio and visual signals Low battery warning Completely portable Fast warm-up time and immediate recovery Powered by 1pc 9-volt battery (included) Made in Japan