About the product: Designed for use by patients having a peak flow below 370 liters per minute. If your peak flow is above 370 liters per minute, you should use the adult (standard) version of the SpiroFlow. It measures (PEF) peak expiratory flow which is a valuable indicator of lung function and changes in asthma conditions. Peak flows may NOT be used to completely evaluate lung function. Comes in assorted colors.