Concrete Single Expansion Anchors are designed for anchoring into concrete, brick or block base material. Inserting a machine-threaded bolt into the anchor expands the Single Expansion Anchor against the concrete at a single point. It is made from Zamak, a non-rusting material, and is available in diameters ranging from 1/4" to 3/4". The single expansion anchor is set flush with the base material and is considered a light to medium-duty fastener.