This low-profile MF hex nut is a thin jam nut with a reduced height, made from plain steel. It's manufactured to DIN 439-2 and ISO 8675 standards and features a fine metric thread. Rated at strength class 04 (040) with a lower load capacity, this nut is designed to keep other nuts from vibrating loose. Plain steel is steel without any coating or surface treatment—it's a strong material, but on its own it offers little resistance to corrosion.