I have limited bar space on my commuter and have more stuff than I have space to put it so I needed an option. I liked the simplicity of this option over the Purely Custom accessory mount, even though it puts an item in essentially the same place. The construction sold me.

I bought one, intending to put my Garmin Oregon 450 GPS on it when I wanted to track a road ride.

It didn't work. The mount for the Oregon 450 is too wide for the Paul mount. I had to rework my plan and so I put the light on it instead, and it fits perfectly.

Paul Components Stem Cap Light Mount

More pictures and description of the details on my site.

Paul Components Stem Cap Light Mount Review | The GPS Geek

It would probably still work fine for a smaller GPS like the Edge models which use a different mount. But since all the handhelds seem to use the same mount now, I don't think any of them would work with this stem cap mount.