About this item Wide operating voltage range allows it to work in most area. High efficiency goose pipe design, you can adjust angle randomly, convenient for use. The cool blue light activates the whitening gel and oxidizes the pigment of the teeth through dentin tubes in the short time, discoloring the teeth to sparkling white both externally and internally. It works silently and will not do harm to your teeth. Digital display with audio feedback, high multi- arch teeth whitening system.