In neutral position the piston rod of a gas push spring is always slid out. The gas pressure on both sides of the piston of a gas-push spring is equal.
This gas is compressible. With sufficient external force on the piston rod, by pushing on the piston rod into direction of the cylinder, the piston will compress the gaz. Due to the intrusion of the shaft into the cylinder the gas pressure will rise. When the external force reduces, the pressure will return the piston into its original position.
Normally, the standard gas push springs should be mounted with rod pointing down, so the seal is lubricated for a maximum life. Other orientations are possible with an additional oil chamber
from 10 Newton (=1 Kg) to 10.000 Newton (=1.000 Kg)