The sensors do not stay in the watch and there is nothing to hold them in place. My first sensor broke before i could even use it $30 down the drain. My second sensor fell out while I was sleeping and has disappeared. Therefore another $30 down the drain and another month of not using this watch. I bought the OV-Watch brand. I followed the directions clearly. my husband even tried (and he's a doctor!) They sensors were OV Watch sensors so i would expect them to fit like a glove. I expected wrong. I would not recommend this watch to anyone. I is so frustrating / upsetting that ths watch was so poorly designed I will even post a video to show how the watch sensor does not fit in the watch.