How To Measure a Topog-E Gasket Please watch video on how to measure Topog-e Elliptical and OBRound Steam Boiler Gaskets. Click a link below to see all measurements available for the different shapes. Hand Hole / Manway Boiler Gaskets Click Here for Topog-e Elliptical Gaskets Click Here for Topog-e OBRound Gaskets Click Here for Topog-e Round Gaskets Click Here for Topog-e Special Sizes/Shapes Click Here for Topog-e Full Sheets of material