Rossmax Peak Flow Meter is used to measure peak expiratory flow rate (PEFR), an important indicator of your lung function. Peak Flow Meter should be used for monitoring respiratory conditions such as asthma. Taking peak flow measures every day and keeping a record of the peak flow measures in your "peak flow diary" can help you and your physician make important decisions about your treatment. You should use this meter and set its color zone indicators according to a treatment plan developed for you by your physician. This compact, lightweight and portable peak flow meter from Rossmax has built-in flexible three-zone management system. It also has easy to read numbers with a measurement range of 60-800 L/min. This meter was designed to make following your asthma treatment plan easy. Your doctor will set the color zone indicators to your personalized zones based on your personal best peak expiratory flow rate value (the best peak flow value you can achieve).