Package details:
20Pcs M4x20mm
20Pcs M4x25mm
20Pcs M4x30mm
20Pcs M4x35mm
20Pcs M4x40mm
80pcs M4 Spring Washer
80pcs M4 Nuts
80pcs M4 Flat Washer

About Countersunk Screws:
The countersunk screws are mostly used in places where the surface of the parts cannot be raised after installation. The parts to be fastened are thick and thin. The so-called thick, that is, the thickness of the parts to be fastened is larger than the head of the countersunk head screw. Thickness, after the screw is tightened, a part of the screw thread does not enter the threaded hole.