Upgraded piston heads usually have holes on the front face of the head. When the piston is moving forward, air goes through these holes and forces the surrounding O-ring outwards to create a seal for preventing air leakage.
The number and position of the holes do matter. You want to have at least 4 holes, and based on our experience there is no need to have more than 8 holes.
With a One Way, when the piston is retracted by the spring, the O Ring retains its original size so piston movement can be made easier and smoother. When the spring is released, the piston is pushed forward, and the air it faces flows through the holes to the inner side of the O ring, effectively “expanding” the O ring to a size that can provide better air sealing effect.
