This screw with a knurled head made entirely of polyamide is called the PLAS 87, a part exclusively manufactured by Bülte. They are easy to tighten and they are particularly suitable for places with little space and where fixing with a tool is made impossible.
The PLAS 87 knurled head screw can be screwed in by hand.
Lengths 15 and 17 mm have a 5.0 mm non-threaded part under the head. Most screws fully threaded up to 80 mm long.
Exclusive Bülte part, they are often used in industry, mechanics, and aeronautics...