Manually operated Rheodyne 7-port valve has a center port that connects to any of six peripheral ports by rotating the handle. Low dispersion. Internal volume <2µL; I.D. 0.41mm. Use for mobile phase selection or for connection to one of up to six columns. For the latter application, two valves are required, one to connect the injector and the column(s) and the other to direct flow from the column outlet to the detector.