Perfect solution to ensuring a bolted joint will not self-loosen even under the most extreme conditions Wedge lock washer M10 Prevents loose screws and nuts Specifically for manifolds and turbochargers Finally a solution for loose nuts and screws. Specifically at the exhaust manifold, exhaust manifold and turbocharger nuts and screws tend to loosen by vibration and temperature fluctuation. This can be prevented with the help of the patented two-shim screw retainer. The two shims lock against each other by their angled surface and hold screw or bolt tightly even during thermal expansion. You are buying 1 piece only! Material: Stainless steel Inner diameter: 10,5mm Outer Diameter: 13,5mm Thickness: 2mm