I bought the Polar strap, initially it worked fine, but it eventually became as useless with nothing but spikes all the time as the Garmin soft strap it replaced, so I went back to my Garmin hard strap that has been faultless for about 6 years. Then this year I left it at home on a "600" so went to a shop enroute and bought a Giant strap and transmitter and after about 6 months it too is working flawlessly.