These Forgefix high-low thread Concrete Frame Screws are Zinc Yellow Passivated for increased corrosion resistance. They offer a stress free fixing, allowing close to edge applications. They are through-fixing, eliminating the need for marking and re-positioning when fixing batons etc. The Torx compatible head of the screw enables increased torque control. Comes with a Torx compatible bit.Extremely popular fixing for window and door frames. Also now used as a versatile fixing for various applications in DIY, Joinery, Plumbing and Electrical trades. The Zinc Yellow Passivation process of electroplating is similar to the Galvanised and Zinc Plated processes but also incorporates a yellow dye. This offers an aesthetically pleasing finish, whilst having excellent corrosion resistance. By design, TORX compatible head screws resist cam-out much better than Phillips or Slotted screws. Where Phillips heads were designed to cause the driver to cam out, to prevent over-tightening, TORXcompatible heads were designed to prevent it, and consistently achieve a desired torque. The compatible head sizes are described using the capital letter T, followed by a number. The smallerthe number, the smaller the point-to-point dimension of the screw head. Only the proper driver can drive a specific head size without risk of ruining the driver or screw.Ideal holding power in wood due to their alternating high and low thread heights.