2 Rear Window Lift Support Gas Strut For 02-04 Ford Explorer Mercury Mountaineer. Gas charged lift supports are energy storage devices that create energy by compressing gas inside a cylinder. When closed, the energy is stored. When opened the energy is released to raise a hatch, hood, liftgate or trunk, holding them safely in an open position. Lift supports normally store a gas charge of 1,500 psi, therefore, they cannot typically be compressed by hand. By design, all gas charged lift supports begin to fail over time. The most common causes of failure include loss of gas pressure due to natural permeation, exposure to extreme temperatures and frequent use or cycling of the part. Replacement can also be expected if the vehicle is of five years of age or older. Be sure to have your lift supports replace with our aftermarket lift support for the best performance.