Stackable Design: The center of the air outlet is adjustable, rotate it to change the amount of air. Removable Unit: The white plate of the air vent is removable, making it easy to clean. High Quality Material: Made of high quality ABS plastic, the air vent is compact and stable. Easy Installation: With the reverse buckle device, slide the air vent cover into the previously opened hole, then rotate a little to fix it. Connect the tubes and lock them with hose clamps Wide Application: The disc valve can be installed in inside as air inlet and outside as air outlet, compatible with 75mm diameter sewer pipes, can be mounted on wall and ceiling.