Durable, portable, and accurate. The Assess® Peak Flow Meter provides an objective measurement of peak expiratory flow (PEF), a valuable indicator of lung function. Assess enables the nurse to better manage children with asthma. Assess helps asthmatics maintain appropriate medication levels and provide a warning of impending asthma attacks. Manufacturer's Warranty: One year free replacement should the Assess Peak Flow Meter fail to operate for any reason. Single patient use.