The amazing EDC-Key by Maratac™ was developed by EOD Robotics in 2008 for use by military robotics repair technicians.
Effective, as lightweight as practical, and budget friendly.
Standard bits and extensions fit into the plastic holder very well. The interior of the plastic holder is tapered, in order to hold bits in very well.
I recommend this to my friends, and to all handy-people.
When trying to unscrew something in a tight space, I can pop one of these caps on the end of the extended bits from my screw driver and get the job done. I also keep a full setup in each of my tool sets.
I would not say it replaces a real screwdriver but does it come in handy in a pinch.
It's a handy tool, but the magnet inside the bit holder seemed to be crumbling. I noticed bits of something stuck to the bit when I first got it. More and more came out everything I pulled the bit out of the holder. I kept the tool on my keychain, but when I finally needed it the bit was missing because it fell out. I had to order another. It's in expensive but still a drag.