Features; • External teeth expand and grip into the material, giving high load bearing strength • Designed specifically for use with wood and chipboard screws, the internal ribs interlock with the screw’s thread to provide a secure fixing • Increased installation safety • Wide range of applications • All steel, non-flammable fixing conforming to BS 7671 standard’s 18th edition, which requires wiring systems to be supported by materials which are unlikely to prematurely collapse in the event of a fire.