I love the Cobra indoor volleyball net system.  It is amazing how easy it is to set up and take down.  We use it in our Family Life Center and it's so non invasive that it's basically invisible.  Unless your'e looking for the sleeve (insert kit in the floor) when you're setting up the system, you would never know it's there.  Everyone is amazed that the equipment is so stable and sturdy yet has such a small (about 1" diameter) footprint in the floor. 

I have attached pictures of our insert for the Cobra.  (See below - the insert is the round grey circle in the middle of the picture.)  The tiles (interlocking tiles sportcourt flooring) we have on the floor are 1 foot by 1 foot and the lines that are painted are 2 inches wide, maybe this will help others visualize the scale and how non-invasive the insert is.