Most T-1 and T-2 models have a round air intake opening in each door opening. This sponge rubber ring is glued to the body to give a good seal when the cover is in the closed position. The original of this seal is often disintegrated, so replacement is a must.

A secondary use for this seal is in the Zenith air cleaner canister to stabilize the cartridge; two seals is about the right thickness.