I am selling this one. It is a few years old but very lightly used. One thing that makes this model useful for tennis players is that it has a average heart rate feature and another feature which can record heart rate samples from intervals as small as 5 seconds to 5 minutes apart. 15 second samples allow enough memory to record data for over an hour. This really helps in tracking your heart rate during sprints and your recovery between points. Of course in addition it is loaded with other features such as warmup and trainning heart rate zones with audible alarms, heart rate recovery time measurement, 30 lap stop watch memory with heart rate at each lap, ten target lap times, difference between actual and target times for laps, calorie counter, and accumulation of exercise stats over multiple sessions. This one has no computer interface, the settings and data display are all on the receiver. I have the receiver, transmitter, chest strap, full manual, bike mount, and original box. I'm selling this one for $50 shipped.