-Private version： A user code can be used for long-term, suitable for personal applications.
-Public version： Enter a user code to lock and unlock once only and then user code will be override, suitable for public applications.
-User code can be 1 to 8 digits in length，100000 of possible combination.
-Powered by button-cell battery, life time up to 1 year, automatic low battery warning.
-Board thickness 16-25mm
-Steel plate thickness 0.5-3.0mm
