The M4-0.7 x 12W9 JIS B1188 Phil Pan 304SS Split Washer 302/304SS Flat Washer Sems A2 Stainless is a high-quality washer set designed for use in a variety of applications. The split washer is made of 304SS stainless steel and is designed to prevent loosening due to vibration. The flat washer is made of 302/304SS stainless steel and is designed to distribute the load of the screw or bolt. The set is RoHS compliant and meets JIS B1188 standards.