Gas Spring Assy holds the ABI 3900 Chamber Top up. Excludes Ball Socket Ends. These are needed to attache it to the instrument. However the Ball Socket ends can usually be taken off the old gas spring and reused on the new gas spring. Before ordering you should make sure you can reuse the old Ball Socket ends from the old gas spring. If you cannot reuse the old ball socket ends you should order PN: 295-101554.