The Oxyll selector dual device has been designed by Hersill as a highly effective and accurate flowmeter. In order to save time and oxygen, it features a revolving control knob which allows the user to exchange between the direct exit and the nebular device, face mask or humidifier, without interrupting the oxygen supply in the meantime. The body of the device is made from chromium-plated brass, the ball from stainless steel, and the inner and external tubes from polycarbonate. It weighs 670 g with dimensions of 145 x 145 mm and is virtually maintenance free. The flow rate is 0 to 15 l/min.