uniFAST black cylinder head screw, martensitic stainless steel, black 4,5x50

Stainless steel refers to alloyed or unalloyed steels that contain at least 10.5% chromium and less than 1.2% carbon. Colloquially, stainless steel is also referred to as stainless steel (NiRo), although not all stainless steel is the same as "stainless".

TORX (from the English word ‘torque’) is the registered word mark for a screw drive profile, the standard designation for which is ‘internal six-lobe’ (English: ‘six lobe, internal socket’). With the six-lobe internal socket, the screw and tool are subjected to less radial stress than with the traditional internal hexagon, and consequently suffer less damage. Torque is transmitted more directly via the radial parts of the tooth flanks rather than via the faces of the hexagon.

Stainless steels are defined in DIN EN 10088-1 as iron alloys containing at least 10.5 per cent chromium and no more than 1.2 per cent carbon. The multi-part DIN EN ISO 3506 series of standards applies to mechanical fasteners made of stainless steels. C1 has low impact strength and ductility. Caution is advised when using C1 at temperatures below freezing. Martensitic steel grades are always highly magnetic.