Asbestos Packing Sleeve washers are superior. This Grafoil flexible graphite sealing material is made from pure, natural graphite flake. These gage glass washers provide a tight seal while maintaining their flexibility and resistance to the harshest environments such a heat, corrosion, and aggressive materials. With a superior sealability under low flange loads. High surface conformity, and an unlimited shelf life. Grafoil gage glass washers have a temperature range up to 800 F. We have two major brands Bishop and Challenge 30 x 30mm30 x 31mm31 x 33mm Gauge Glass Washer Sizing Chart: A Inside Dimension of Washer, B Outside Dimension of Washer, C Thickness of Washer