are you talking about the little bal levelers that cradle a tire, and lift with a jack screw? they have a weight limit, and can only go with so big of a tire........ I'm not sure off hand what the numbers are though, but I think a 5th wheel might likely be too much for it. I know about them being used for pop-ups and small single axle trailers....and I actually have one in my attic leftover from my pop-up. I'd like to find a good home for.....