RS PRO M4 Alumina Ceramic Washer (9 x 4.5 x 0.9mm) A high quality and tough M4 washer featuring an internal diameter of 4.5mm, an external diameter of 9mm, and a thickness of 0.9mm, constructed from Alumina Ceramic for excellent wear resistance, corrosion protection, outstanding hardness and strength.;Alumina Ceramic washers offer several advantages over other types of washers. Suitable for operating in temperature extremes and featuring excellent resistance to chemicals along with high mechanical strength the Alumina Ceramic washers are ideal for operations in harsh and challenging environments where regular maintenance isn’t always possible.;Built to comply with British Standards BS 4320:1968 these Alumina washers are ideal for a wide range of environments and are used throughout industry including manufacturing, automotive applications, aerospace and for use with processes where metal washers are not suitable. Features and Benefits Alumina Ceramic Washer Metric size M4 9 x 4.5 x 0.9mm Narrow design High level of temperature and chemical resistance Standards and Approvals: BS 4320:1968