RFPL type pneumatic cage-type single-seat valve is a top-guided, three-flange valve with a protective sleeve, designed to prevent flash and cavitation damage to the valve body. The fluid channel features an S-shaped streamline, and the valve plug has two characteristics: equal percentage and linear. Each specification has three Cv values. By changing the plug and seat, the valve can achieve different characteristics and Cv values. The valve has a simple structure, strong interchangeability, and a wide range of applications.