This competition designed gasket is for bore (4.250 to 4.370") usage on 1991 and later "Gen V & VI" Chevrolet Big Blocks with aluminum heads. It is a preflattened wire ring. The nominal compressed thickness is .039" with compressed volume of 9.7cc. These are composition design gaskets. Technical Notes: This gasket is for "Gen V & Gen VI" engines only, (1) gasket per package. These gaskets contain stainless core for saltwater marine use. **Refer to Technical Note on P/N 14015351.