Type BP Back-up Rings have a rectangular cross section and are made from PTFE materials. The cut angle is either 30˚ or 45˚. It consists of standard two spiral windings which are cut at the ends at an angle. It can be used in static or dynamic applications with reciprocating movements possible. Preferred for installations in closed grooves where uncut Back-up Rings are not suitable. It can compensate large temperature changes and tolerances through a screw-like elongation and contraction.