Ultra-Seal Valve Cover Gaskets Fits 1959-1980 Chrysler 361,383,400,413,426,440 B/RB Big Block except 426 Hemi Mr GasketUltra Seal is Mr. Gasket premium valve cover Gasket material. It's manufactured from a high density cork and rubber blend with a black latex coat applied to the outside to help seal minor flange irregularites and eliminate oil leakage. It creates a positive seal by controlled swelling of the Gasket material when exposed to hot oil. For original equipment replacement, high performance street, drag race and oval track use. Sold as a pair, these Gaskets