<VV> bumper struts-no corvair

[Harry Yarnell]

My question is, what's inside the bumper struts on a modern GM car?
Bumpers (facsha) on newer GM cars are held to the body by collapsible struts. Is it oil filled? Springs?
A current project requires two of these to be modified, and before I get out the torch and/or the saw, I need to know what's inside.

harry yarnell
perryman garage and orphanage
hyarnell1 at earthlink.net