Here is a picture of the one we have, a local feed store sells these and I bet they've sold 40-50 of them and I've never heard of any complaints. Our's has a single pipe down the center (its 12" or 14" in diameter) with 5" cross pipes bent in a very slight U shape to cradle the bales. The trailer rides on an old semi trailer axle, I think in over ten year's we've replaced two tires but even with one flat tire it will easily handle the weight of a load of bales. I like having the truck axle instead of a normal running gear because it's more durable, it's easier to get around and it transfers some weight to the tractor. Our's has a heavy clevis hitch on it with an adaptor that lets you slide a pintle hitch ring in it and then the bale stabber has a 2" vertical pin mounted on the bottom that slips up through the ring so you can hook and unhook the trailer without getting off the tractor.  Alot of the newer trailers like this he's been selling have another set of cradles over the axle so they can carry 8 bales and a gooseneck hitch, both of which I wish our's had.