The internal square pile holders are made from 3" x 3" x 1/4" angle and have four 6" rollers included. The pile holder is hot dipped galvanized after fabrication. Removable means that one side is removable, useful for using on your dock when you have existing piling. However, it makes a weaker frame because you have to build, or cut the frame around the pile guide. You also need to place in locations where there are not floats (if you are using floats)