Hi ! I have the Microlife Digital Peak Flow Meter. I ordered it off of Amazon. I like it to keep track of how I'm doing. If I feel like I'm having a bad breathing day, I will use it and see if my numbers are down. I also try to monitor at least once a month, just to keep a record for myself to show my doctor if I feel he needs to see the numbers. I think there are many different ones out there. This is just what I got. I hope this helped! Best, Jackie (Moderator)