The Systema Piston Head with Bearing is designed to draw up the BB into the loading chamber by changing the number of air inlet ports controling the negative pressure that builds up in the cylinder when the piston retreats.  By rotating the tip of the cylinder head’s bumper area, it is possible to change the air inlet ports from 3 up to 6 open ports.  In addition, the silicone o-ring (white) add an additional benefit of better cold weather performance!