This is the #300 with cord cemented into the corrugations. Metal thickness is about .019" or .020". Corrugation pitch is 5/32", 3/16" or 1/4", according to gasket width or application.

 

Approximate overall gasket thickness is 65% to 70% of pitch. #305 is a highly effective replacement for millboard gaskets on large-diameter flanges which handle flue and combustion gases at temperatures up to 1150 deg F (depending on the metal) under light pressures.

 

Frequent breakage is a recognized problem in the handling of millboard gaskets. #305 gaskets withstand pressures to 600psi.

 

They are not suited for vacuum or oil service.