These gaskets are made from a heat resistant compound that is flexible enough to allow proper expansion of the
molded lip against the glass. Correctly installed, with lip toward the bottom of the stuffing box, the applied pressure will force the lip tightly against the glass forming an effective seal and at the same time cushioning the glass from the metal. The outer wall will simultaneously expand against the stuffing box nut preventing pressure escape from the outside. The washer section is made thin enough to allow the glass to become adjusted to its proper alignment without any danger of breaking. In installing Marvel gaskets the nut should be made up thumb and finger tight. A wrench should NOT be used.