proton

I see a lot of people who have bought a Hydrogen Proton ball machine list the #1 thing they love about it is the size and weight. With that in mind, I was wondering if anyone can you expand on this and is it really that big of a concern because here's the way I'm currently thinking about this...

I'm currently in the market for a ball machine as my 3rd grade daughter is picking up tennis quickly and I'd like to use it as cardio exercise. I was originally considering the Slingerbag, but the price increased several times the past few months and now at $800 I don't feel its worth it for a...