The Brand, pilot check valve is precision built, dependable and low priced. In one direction oil opens a check valve and passes through the valve and into a cylinder. As the check valve closes the oil is positively trapped in the cylinder with a check ball valve. Applying pilot pressure to the pilot port of this valve moves a piston stem against the ball to push the check ball off its seat thus allowing the oil to leave the cylinder. The PC is intended to be a positive safety check, it is not intended to be a metering or counter balance valve. The pilot piston ratio is 3.2 to 1 (PC37C and PC6C) and 4.0 to 1 (PC50C and PC8C), this means that it only requires 0.312 and 0.25 as much pressure on the pilot piston as is being trapped in the cylinder by the check ball.