will it hold a Polar heart monitor?

That's a loaded question. It completely depends on what HR monitor you have, its design, etc. I highly recommend a call to Polar's customer service and ask them what your options are. Have your model # ready so they can easily look things up.

I wouldn't be surprised if this did work with your HR monitor, if you feel like taking a little risk you can buy it from Backcountry. If things don't work out, send it back and Backcountry's killer return policy has you covered.
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