The Skid Rollers are a U Fab product that I ordered from eTrailer, I've seen several vendors that carry that line. They come in different sizes, I got the biggest ones I could find. (3X2X3) I was really impressed with the quality. If you look closely in the first photo you'll see the internal bearings, bushings and wet bolts with a nylon nut. (Thanks Dave I learnt a new term from your earlier post today) I hand packed the bearings but I'll be able to keep them wet with the grease zerks.
The installation instructions were very vague...
"Weld on skid rollers to any location that drags on the ground for any type and size vehicle/trailer."
So I welded them as far back as possible to the bottom of each frame rail.
(I in this sentence means I helped/watched my friend that's a shop manager weld them)
After bending a pair of scissor jacks in my old trailer and a close call in my new one...
I figure it's a wise investment!!!