They say Treated lumber and aluminum is a big no no, Causes some kind of reaction in the aluminum. Im not convinced as mine is fine after 3 years. My dad has these plastic things that go around his wooden bunks and it is so slick that he hates them. When you load the boat and nose it up, if you let off the throttle before you hook the bow up it will slide right back down. His is glass though, it would probably work better with aluminum