Series 966 Valves in-house design to outperform loose liners. Butterfly Valves elastomer liner is molded directly in the body bore and vulcanized in-situ, making it last the entire life of the valve. The result - a valve that requires no form of maintenance. Butterfly Valves are ideal for precision throttling and on-off applications, especially in lighter-weight piping systems. Outstanding throttling accuracy for process control has been achieved through low-friction, erosion resistant sealing surfaces with very low operating torques.