The KTR fouling ring is made of special PTFE material. In the piston hole, the main seal should be used with the hole and the guide ring should be used. Through the particularity of PTFE resin, foreign matter in the operating oil can be absorbed and cleaned up, and the service life of other seals in the sealing system can be increased. The open form is easy to install, and it is equipped with an oil discharge port to prevent the deformation of PTFE resin and blocking the oil passage during pressure.