Powers Fastening Innovations 05511 Spike Anchor - 3/16-Inch by 3-1/2-Inch Mushroom Head Grade 8.2 Carbon Steel Pre-Expanded Anchor, 100 Per Box One Piece, tamper-proof anchor for use in concrete, block, brick or stone Formed with an "s" shaped configuration at the working end of the anchor to create an expansion mechanism 100 per box