Found under the following brands:
Unoair, Square D, Watts, WEG, Champion, ACS, Hosetract, Hubbell-Furnas, Kellogg
(38602) High Temperature EXHAUST Flange Gasket. Use only if standard exhaust flange gasket keeps blowing out. NOTE: coat each gasket with a thin layer of Loctite on each side of the gasket when installing.