Non Asbestos O-ring Gasket for Sight Glass is also named non asbestos gasket , Asbestos free gasket and cushion joint, which is made of high pressure aramid fiber mixed rubber sheets. It is a new material for the sight glass sealing as a general purpose gasket material suitable for service in hot water, mild acids, alkalines, It can resistant the temperatures up to 450 °C and the pressure up to 150 bar.