Powers Lokbolt 3/8" X 3" Hex Head As All Steel Sleeve Anchors (50/BX) (05020S) are pre-assembled single unit sleeve anchors available in carbon steel and stainless steel which can be used in concrete, block, brick and stone. The Lok-Bolt is designed to draw the fixture into full bearing against the base material through the action of its unique and flexible compression ring. This helps to increase the resistance of the anchor to loosening when subjected to vibratory loads. As the anchor is being tightened, the nylon compression ring will compress if necessary, so that the fixture is tightly secured against the face of the base material. Under load, the specially tapered plow bolt is drawn further into the expansion sleeve to develop increased locking action against the walls of the holes. Extension sleeves are added for longer lengths.