These valves are designed to replace metering and non-metering cartridges within existing Acorn Penal-Trol, Metcraft Tempus II and Willoughby Temp 1/Temp 2 valves to pneumatic operation. The Retro-Air valve assembly package consists of the Retro-Air servometer cartridge, a push-button assembly (or adapter) and polyethylene 1/8" tubing to connect the push-button to the Retro-Air servometer cartridge, which replaces existing push-buttons and push-rod hardware.