Compatible with the following models:<br> FitBit Alta<br> Fitbit Alta HR<br> fitbit flex 2<br> FitBit One<br> FitBit Zip<br> Fitbit flex<br> any fitness watch≦ 1.7inch*0.8inch<br> <br> If you are not completely happy with our product, send us a mail, we will give you refund within 3 month or replacement within one year.