ACCELS Performance Replacement GM Opti-Spark II Distributor is a direct plug-in factory replacement with an aluminum housing and a high-dielectric-strength, glass-reinforced cap. Both the housing and the cap are sealed to keep out debris and vented to eliminate corrosion and dissipate any heat that is captured internally. The cap has brass contacts and is epoxy overmolded to eliminate arc-over, and the rotor blade has a special coating that resists corrosion and extends its life.