Zinc Aluminum Mini Two Bolt Flange Mounted Unit Bearings with Eccentric Locking Collar (KFL) have stainless steel housings and stainless steel inserts. Bearings that are mounted within a flanged housing are used when the bearing mounting surface is perpendicular to a shaft axis. The housing is bolted to a foundation through the holes in the base. A set screw is a type of screw generally used to secure a bearing race to a shaft. Set screws are most often headless (also called blind), meaning that the screw is fully threaded and has no head projecting past the major diameter of the screw thread. It exerts compressional or clamping force through the bottom tip that projects through the hole.