Asahi/America Inc. has introduced the Type-21a Seat Support Technology (SST) flow control ball valve. This true union ball valve offers all of the robust elements of the Type-21 and the ability to precisely control flow. Available in 1/2-inch through 2-inch sizes, the SST ball valve features a precision-machined PVC ball with center provisions to support PTFE seats from 0 to 100 percent of capable flow. The Type-21a SST ball valve produces equal percentage flow characteristics for fine throttling. The valve requires directional installation and comes equipped with a flow direction label.