The M4 x 16W9 JIS B1188 Phil Pan Split Washer Flat Washer Sems M/S Zinc is a type of fastener that is used to secure two pieces of metal together. It is made of zinc-plated steel and has a split washer and a flat washer attached to it. The split washer helps to distribute the load of the fastener, while the flat washer helps to prevent the fastener from sinking into the material. This type of fastener is often used in automotive and industrial applications.