The Brand, HPV4 directional control valves are small and compact. The HPV4ís were designed primarily for use with hand pumps and other low flow applications where size weight and appearance are important. Three-position detent (D) holds the spool in neutral or either active position. Closed center (standard) blocks all ports when in neutral. Tandem center (T4) sends oil from P to T when in the neutral position. The T4 spool should not be used for flows of 4 gpm and greater because the pressure drop increases significantly.