This Teflon-coated gasket has solid pre-flattened wire O-rings around each cylinder. It is highly recommended for competition engines 4.00 to 4.125 cylinder bores.Compressed thickness is .041". This gasket does not require retorquing. Drill steam holes when using this gasket on 400ci small-blocks. This gasket has a bore of 4.166" and compressed volume of 9.1cc.