The solenoid air operated spool valves in the ASCO series 541 are designed for quick and easy installation and operation. The compact design allows for space-saving installations and the subbase mounting system provides versatile options for connecting to a variety of different piping arrangements. The valves are suitable for use with media such as air or neutral gas, whether filtered or lubricated, and are constructed with a zinc die-cast body and nitrile (NBR) seals for long-lasting reliability. The addition of manual spool position testers allows for easy monitoring of valve operation. The subbases can be easily joined together for multi-valve systems, making the ASCO series 541 a versatile and convenient solution for controlling air and neutral gas flows.