STANDARD action gas lift pistons. They are designed to hold the door ONLY in the fully OPEN postion. They do not hold in intermediate positions.Simple Snap-on 'Ball & Socket' type fitting action. NB - THESE PISTONS WILL NOT REPLACE THE OLDER SALICE/STABILUS TYPE PISTONS THAT FITTED WITH SCREW BOLTS AT EACH END!!! The old type are no longer available from Salice.7 Strengths Available: