IMO, save your money. I don't think they can withstand heavy punching.. ie, they'll teder over.

It's DEFO not worth $300.

You know what, go pick up a 40-50lb bag and hang it from your ceiling. Just use tapcons to achor it into a concrete block. And keep you blinds closed!!! It should be perfectly fine with plenty of hanging strength. For $300 you could buy a great bag and a wicked hammer drill and have plenty of cash left over.

Or get a bag and stand.