This hose is 50 feet long and has a 3/8 inch inner diameter. It's equipped with MPT fittings at both ends and accepts 1/4 inch FPT fittings. You may not combine 25 or 50 foot lengths of the 3M Supplied Air Hose W-9435. Supplied air respirators require a source of clean breathing air such as plant air systems, low pressure pumps, or bottled air. Complete systems include a supplied air hose, an air regulating valve, a breathing tube, and a helmet, hood, or other facepiece.