I saw them on an SOB unit at CW recently. While they were solid, like TCN said, they were on a hard surface to no telling how well they'll work on grass. One thing I don't like is that they "close" inside the rig, so any dirt/moisture that's on them will get inside whey they are closed. I'd also be concerned about them jostling around while traveling as they could do a lot of damage awfully quickly if they came loose.
All that to say, DW loved them so you never know - happy wife = happy life