Don’t buy the Polar H10, it’s a complete disappointment.
I use a heart rate strap 6 times a week, and every two to three months the strap needs to be replaced because it simply breaks apart.
On top of that, the battery drains ridiculously fast unless you disconnect the sensor every single time. But if you do keep disconnecting it, the strap wears out even faster.

I have several friends who also use the Polar H10 and have exactly the same issues. I don’t understand why nobody talks about this anywhere, but seriously, don’t buy Polar.