Automatic Transmission Extension Housing Seal (710928) by National®. With Dual Lip. Width: 0.5″. Inside Diameter: 1.938″. Outside Diameter: 2.685″. Housing Bore: 2.68″. Don’t just repair a leak, prevent future problems with a National Oil Seal. This part is manufactured using exclusive National Dynamic Edge technology that generates a dynamic pumping action to keep harmful contaminants such as dirt, moisture, etc. out of the seal and other wheel-end components.