For example, for the same DN of a flange, it means cutting different gaskets of different outer diameters, corresponding to the 4 bolt hole diameters, associated with the bolt positions. Latty has ...

Moreover, flanges must be cleaned before reinstalling them, as well as fitting new gaskets and properly tightening the nuts and the bolts that hold them together.

Brian C. Lehr, Applying Gasket Materials to High-Stress, Dynamic Flange Environments, SAE Transactions, Vol. 109, Section 6: JOURNAL OF PASSENGER CARS: MECHANICAL SYSTEMS JOURNAL (2000), pp. 1002-1007 ...

The 52 slip-on flanges, bolt sets and gaskets, versus 60 rigid couplings accounted for major weight increases in the welded/flanged system.

Jess W. Oren, Design Considerations of Deflection in a Rigid Flange Gasket Joint, SAE Transactions, Vol. 92, Section 1: 830008–830359 (1983), pp. 817-828 ...

Earlier gaskets use a larger exhaust crossover opening; that can result in a significant exhaust leak at the flange when using any Pontiac intake manifold (bottom). See All 2 Photos ...