This state of the art tester is simple but precise, giving the user a quick "yes/no" reading Housed in a high impact plastic case, it is everything one needs to test diamonds in rapid succession, whether mounted or unmounted Has a metal alert ( a long beep if metal is touch rather than stone) Large/small switch for testing diamonds over and under eight points Green diamond indicator light illuminates if the stone is a diamond Seven second warm up time with a 150 second shut off alarm If the stone is a simulant nothing happens Has a low battery indicator and it includes a 9 volt battery