I have a set of the GoJak 5000's that were sold on Craigslist. The guy had advertised them as the 6200, I need the extra width.

I bought them and they work great on my epoxy floor, really heavy duty. Great for moving cars around so I can cram as many cars as possible in the garage for storms. It makes it a single person operation, I have not tried trucks, suv's etc. Leaving cars on the dollies is not a problem either.
Not being hydraulic or having to jack up the car first is a real plus.
I have bought a set of the 4500 which hopefully will arrive soon.
I will most likely sell my 5000's in a week or 2 if anyone is interested, sorry to highjack the thread.