Rubber seal is a common form of a device for preventing leakage of fluid from one part of a container to another, whether dynamic or static. It is also called as rubber ring, rubber sealing, rubber seal ring. The catagories of rubber seals includes hydraulic seals(piston ring, rod ring, wipers, guide ring, buffer ring...), rotary seal(oil seal, coolant/water seal...), rubber o rings and so on. Care is needed in design, since poor tolerances can cause extrusion of the seal under pressure.