The excellent quality of the sheet is reinforced by using an aramid and a glass fiber mixture and bonding nitrile rubber. SF 3300 conforms to the highest British standard for non asbestos board sealing materials - BS 7531, X. A retrofit of SF 3500 and SF 3300 was developed for the application of a medium lift pump with high resistance to high surface stresses. If the need for caustic liquid seal, with a blend of aramid and carbon fibers reinforced SF 3300 modified materials: the SF 5000 is widely used in the pulp and paper industry.