Mr. Gasket Carburetor Gaskets ensure an airtight, leak-proof seal and can be trimmed into an infinite number of configurations to modify the port to your exact specifications. Engineered specifically for square-bore 4-barrel Holley carburetors, these .063-inch-thick gaskets are precision die-cut for exact fitment. They ensure optimum torque retention, ideal crush resistance, and excellent sheer strength and seal using minimal clamp force yet still release easily every time. They're manufactured from a durable heat- and fuel-resistant composite gasket material and die-cut for a consistent, precise fit and years of trouble-free service.