These Edwards vacuum Co-Seals are designed to seal ISO flange fittings and are made of a polymer-supported nitrile O-rings, which is suitable for high vacuum down to the 10-8 Torr range. They represent a major advance in the method of sealing NW and ISO flange connections. The seal design eliminates crevices and trapped gas volumes (there is nothing between the rubber vacuum seal and the gas media). When fitted, the inner face of the Co-Seal is directly exposed to the vacuum system, eliminating any crevices or trapped volumes, which can generate gas bursts and inhibit pump-down.

Unlike the regular centering ring and O-ring, the NW Co-Seal is fully restrained externally. These Co-Seals are available with either nitrile or fluoroelastomer seals. They can be used for either ISO-F bolted or ISO-K collar flanges, the cut-outs around the external circumference of the Co-Seal are positioned so that the securing bolts or claw clamps centralize the Co-Seal precisely. These Co-Seals are for ISO NW40 flanges and contain a Viton seal and are sold as one each.