Sleeve anchors are expansion type anchors designed for concrete, block, and brick. They have a split metal sleeve that surrounds a threaded stud bolt with a shaped end which expands the sleeve as the nut is tightened. Sleeve anchors are especially useful in hollow block because they provide a larger area of contact with the base material. They are made from zinc plated steel or 18-8 stainless. The available head styles are: hex nut, acorn nut, slotted flat, and slotted round.