Hexagon nuts ~0,8d DIN 934-stainless 1.4529 M20

The wrench sizes for hexagon bolts and nuts are specified in ISO 272: 1982-01. The nominal wrench size on the workpiece (e.g. bolt, nut) is the same as that on the tool. However, there is some play between the two to allow the tool to be fitted without difficulty. The relationship between the nominal diameter d of the thread and the wrench size s is standardised in EN ISO 4014 and EN ISO 4017 for hexagon bolts, and in EN ISO 4032 for hexagon nuts (dimensions in mm).

Material 1.4529 is a corrosion-resistant stainless steel with the short name X1NiCrMoCuN25-20-7. In the American ASME standard, it is designated UNS N08926. Particularly resistant to aggressive media (e.g. phosphoric, sulfuric, or hydrochloric acid). As delivered, the steel is resistant to intergranular corrosion.

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".

The term plain indicates a completely untreated, merely oiled, smooth surface for all DIN and ISO screws such as wood screws, hexagon head screws, threaded rods, nuts and many types of washers.

Stainless steels are defined in accordance with DIN EN 10088-1, and the multi-part DIN EN ISO 3506 series of standards applies. Stainless steels of grade A8 are known as ‘6% Mo’ stainless steels. They offer high resistance to all types of corrosion, including pitting, crevice and stress corrosion cracking. This grade is suitable for use in swimming pools where chloride is used as a cleaning agent and for applications in marine environments.