it looks like UHMW......it comes in black and white as well ...go to a local machine shop and ask them if they have small drops that you may purchase.....its not that expensive in drops....or you may want to get them to make you some for your boat ...i will be needing 4 when the time comes....or you may call McMaster Car and see what a length 2"x1"x12" will cost and order it from them......This block is mounted on some type of plastic material that mounts around the stnchion. What is that material and where can I get it?
My guess also, let us know when you find out for sure,I think it is Delrin..