The peak expiratory flow (PEF), also called peak expiratory flow rate (PEFR) is a person's maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person's ability to breathe out air. Compact, lightweight and portable Built-in flexible three –zone management system Easy- to- read numbers Measurement Range 60-800 L/min (ADULT) Range 50-400 L/min (CHILD) Accuracy and repeatability assurance Suitable for use with disposable mouthpiece Washable ,