Galvanized steel
A two-threaded stud or plumbing screw is used for installing drain or sewer pipes, as well as other plumbing products (water supply systems, washbasins, toilets, etc.).
The plumbing combination screw has not only different types (screw-screw, screw-screw, screw-screw) and sizes, but also different installation methods (using an Allen key on the metric side of the screw or an Allen key used between the threads of the stud).
This type of fastener is made of carbon steel with a galvanized coating.