N-BK7 Optical borosilicate-crown glass from SCHOTT

Schott N-BK7 Glass bk7 slot N-BK7 is a Schott designation for the most common Borosilicate Crown glass used for a wide variety of visible applications bk77 slot BK7 Cute, KTV microphone, BT , 1200mAh battery for 8 hours of work, support TF card BT playback modes, variety of funny sound effects

bk7 slot BK7 Cute, KTV microphone, BT , 1200mAh battery for 8 hours of work, support TF card BT playback modes, variety of funny sound effects