I've got something similar to that on my trailer (in truth, I have no clue what it looks like, as it came from my builder that way.) This is for flushing the brakes, not so much to protect the hubs.
Basically some plumbing to get water from a hose connection on the frame to each of the brake drums. There, there's some kind of spray head thingie which is attached thru the backing plate, and that saturates everything inside. Mine is a brass hose connector (female), a bunch of clear plastic tubing, and the aforementioned and unseen spray heads. All held on with zip ties.
No idea whether it does any good or not, but since its there, I use it after every trip.
I would bet that you could kludge together something from stuff from the hardware store/garden center for a hell of a lot less than 70 pounds, though.