I have a set of these from Harbor Freight.
http://www.harborfreight.com/cpi/cta...emnumber=93368
They are not bad, but with the full bodied truck on them now it is sometimes a bit awkward to move them by myself, but my floor is not always the cleanest. It's only a pain so to speak when you have to change directions. Until the wheels realign it's tight.
I must say until I got all the body on and engine in they were great.