The M4 x 8W9 JIS B1188 Phil Pan Split Washer Flat Washer Sems M/S Zinc is a type of fastener that is used to secure two or more pieces of material together. It is made of a 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 and prevent it from loosening, while the flat washer helps to protect the surface of the material being fastened. This type of fastener is commonly used in automotive and industrial applications.