Open center. Four 3/8 -16 mounting holes on 3 1/4'' B.C. . Valves are available in two different load circuit options: Load Reaction - Steering ports are blocked in neutral, locking the axle position when the operator releases the steering wheel. Steering ports are tied together in neutral, allowing the axle forces to return the steering wheel to it's original position when the wheel is released (similar to steering in an automobile). *Reaction Load *Max PSI 2500 * CU. IN Displ 4.5 * GPM Flow 4-8 * Port Size SAE 8