Single expansion anchor is also called machine bolt single expansion anchor, or concrete single expansion anchor. It's an internally threaded, mounted anchor for light to heavy duty. It's used in hard and dense base materials such as: concrete, brick block, mortar. The body of the anchor is made of Zamac, so it's highly corrosive resistant. A cone nut and two piece tubular shield preassembled into a single expansion anchor. We use zinc plated carbon spring wire or band to hold the two piece tubular shield together. When the bolt is inserted into the anchor, it expands and turns clockwise, thus produce the friction. The anchors are available in six different diameters: 1/4", 5/16", 3/8", 1/2", 5/8", and 3/4".