The MCM83248 series o-rings are 'fuel proof' FAA-PMA replacement o-rings. Only McFarlane has FAA approval to replace the old, less fuel resistant nitrile (MS series) and synthetic rubber (NAS series) o-rings with the latest fuel proof fluorocarbon o-rings! Flurocarbon rubber is commonly known as Viton. It is an advanced rubber that has extremely good fuel and heat resistance and is ideally suited for aircraft fuel system applications.
