The M4 x 10W8 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 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.