I bought this to replace a 10 year old Polar Heart Rate Monitor that finally kicked the bucket. I figured that this would work pretty much the same way. It didn't. I read the directions and tried it again. Still couldn't get it to work. I bought a new battery for the strap. It still didn't work. I re-read the instructions, thinking that I had missed some important detail. It still wouldn't work.If you want a good Heart Rate Monitor buy some other brand. If you need just a watch this will do the trick for you, but you can find one cheaper than this.