This consists of a head harness, mouthpiece, and noseclip, corrugated breathing tube, Briggs equalizing device, 120 ft (36.58 m) of reinforced air tubes, and a strainer and spike. It has neither bellows nor rotary blower but depends entirely on the action of the equalizer for comfortabIe respiration. The resistance to breathing is so low that reasonably hard work can be done by the wearer over a period of 2 h or more. The air supply tube is attached to the waist by a strong leather body belt.