Accurate heart rate measurement. Some in the reviews write that the error is about 5%, but in my case this is not the case. For 3 weeks, I compared the readings with the good old Polar RS300 chest heart rate monitor in all modes, from rest to severe anaerobe. The pulse is measured exactly 100%. All other indications - oxygen, sleep, stress and so on . there is nothing to compare with, you have to take the manufacturer's word for it. In general, I am satisfied.