linear movement sytem

[Mohammad AK]

hi there
I want to ask a question about hoverglide backpack
In this backpack we see two frames moving relative to other frame
What kind of linear system is used in this structure?
What is its name and its constituent material?

you can see this backpack in this link :

http://www.lightningpacks.com/light..._Lightening_your_load,_lighting_your_way.html

 

[3DDave]

Same answer as last time you asked.