The M4 x 12W8 JIS B1188 Phil Pan Split Washer Flat Washer Sems M/S Zinc Yellow is a type of washer that is used to distribute the load of a screw or bolt over a larger surface area. It is made of zinc-plated steel and has a split washer design that helps to prevent the screw or bolt from loosening. The flat washer helps to distribute the load of the screw or bolt over a larger surface area, which helps to prevent damage to the material being fastened. The Phil Pan head design provides a low profile and a finished appearance.