This is a type F knurled nut, that is to say non-opening (closed). This plastic knurled nut allows manual fixing and clamping. The internal threaded nut is made of brass.
It is therefore a bi-material part, black nylon and brass.
Ideal in machine building, tool making, technical plant construction, testing devices and medical devices, this knurled nut is part of the plastometallic family.