The ball mounts directions say that the mechanism inside is sealed. Says to never use WD 40 in the lock cylinder. Only to use a light lubricant like "air tool oil" that makes sense as WD40 can gum things up. I'll pick up some air tool oil off amazon and keep it handy. My other combo ball unit that I use on my Saab I just took out of its hitch bag to lube it. It was very free. Could push the pin out with my finger. They also make other metals like nickel which are the cheaper ones and probably corrode pretty quick. I think the stainless balls are pretty good.
If the pins on the aluminum mount are not moving freely instructions say its usually due to rust or a drill burr the directions say. That makes sense as my two other cheapo uhaul hitches rust inside the tube like crazy no matter how much grease I use. I can see inside rust easily interfering with the pins operation.
Even the hitch pins on the aluminum mount are stainless.
Here is a link to the stainless convert-a-ball and their other models:
http://www.etrailer.com/p-903b.html
