This Voldyne spirometer/exerciser has a large volume measurement (up to 5000 ml inspired air) and advanced low-work-of-breathing filter. The low-work filter gives you a more accurate measurement of your volume flow since less breath is required to push through the filter. This spirometer/exerciser also features a compact, ergonomic design with built-in handle. Graduations on both sides of the unit plus the good/better/best flow window let you visualize your daily improvement. This is meant only for single-patient use.