Pro Copper Head Gasket for Nissan SR20DE and SR20DET 2.0L Dual Overhead Cam engines. Bore Opening: 3.437″ (87.3mm); Gasket Thickness: .021″; Material: Annealed Copper. *Pro Copper head gaskets require sealant and O-rings in the block or head. For self-sealing copper head gaskets for use with O-rings please see Titan (T916 _ _) series head gaskets. For seal-sealing copper head gasket for use without O-rings please see ICS Titan (S916 _ _) series head gaskets. Package Contents: 1 Piece.