Small Head D = 0.2 inches (6 mm). NO PLUG REQUIRED: Cut into concrete with a small diameter underhole. Clean installation: Due to the tightening process, it will not damage the fixture, and can be installed near the edges or corners of the material. High and Low Thread: High thread with diamond cut (cutout part) to cut the screws into concrete and a screw thread for smooth and perfect tightening without any trouble. Applications: For building materials such as concrete buildings, mortar, blocks, bricks, wood, and other applications, piping, wiring saddles, switch boxes, control boxes, lighting fixtures, bulletin boards, air conditioning equipment, alarm equipment, door frames, shelves, seats. www.iifas.jp