HD 200° wide angle,Anti-peeping,anti-theft,dustproof Deepen the bold thread for smoothness and durability Adjustable length,suitable for door diameter of 14mm,suitable for door thickness of 35~55mm Durable solid copper metal for easy installation,just drill a suitable diameter hole,insert the viewer into the hole,then screw the sides together and hand tighten Suitable for home,hotel,apartment,etc