Abstract: This invention relates to a gasket apparatus for providing a fluid tight seal between a pipe and a porthole in the wall of a manhole riser. The apparatus includes an elongated sleeve of elastomeric material, the sleeve having at one end an outwardly turned, reflexly curved annular flange. The body portion extends axially beyond the flange. A rigid reinforcing ring coaxially engages the inner surface of the flange, forming said flange to a predetermined outside diameter. This apparatus is inserted into the porthole in coaxial sealing relationship therewith. The flange is radially compressed between the ring and the wall of the porthole thereby providing a seal. The end of the pipe is received by the sleeve which is clamped at the distal end thereof onto the pipe to provide a further seal.The method of forming the seal includes inserting a solid, substantially rigid ring into the end portion of an elastomeric elongated sleeve which thereby determines the outer diameter of the sleeve radially opposite the ring.