4.5 x 63mm. Tri-lock thread and spiral point for easy start. No need for pilot hole, won't damage the timber or work loose. Part threaded to prevent jacking of timber. Net-coat treated for outdoor and decking use and CPT hardened. Suitable for ACQ and Tanalith E treated timber. DeckMark accredited. It is recommended to use Stainless Steel Decking Screws with pilot holes when installing hardwood decking.