High quality variable valve made from SUS304, with features of tight sealing that does not allow a drop of water and zero percent of error. By the way of vacuum actuator connection, you can choose either Closed Base or Open Base. CB closes valve only by the power of the spring of vaccum actuator, opening the valve as vacuum is activated, having the merit of making a quiet start at the initial starting. OB is a mode in which valve closes only with the activation of vacuum, useful for works in which valve's sealing power is important. As the valve is open, it makes lound sounds in initial starting.