The Powers 1/4" X 3" Flat Head Pre-Expanded Anchors (100/BX) (03332) are patented, one-piece, tamper-proof vibration resistant anchors designed for use in concrete, block, brick or stone. The Spike anchor is formed with an "s" shaped configuration at the working end of the anchor to create an expansion mechanism. Since the anchor is pre-expanded, there is no secondary tightening operation required which greatly reduces the overall cost of an anchor installation.