Don't wait for a bump on the head or a pinched finger to replace your liftgate props or rear glass gas struts.
Simply measure your current strut extended from the center of the lower attachment to the center of the upper. Most struts are ball and socket and simply pop off.
To order the proper lifting capacity look on the strut itself for it's rating in lbs.
It's recommended that you replace both struts to avoid uneven lifting and twisting that might damage glass or hinges.
Caution: Support your door or glass with a solid rod before removing any lift supports.