Spool holder for TAZ printers

This is a spool holder that provides a nice vertical feed down from above a Taz or similar printer. How is it different from every other spool holder?

* It holds the spool in its central hole, so it is secure and not easily dislodged.
* The spool holder is concave, helping to self-center the spool.
* There are bearings on the spool holder, so that it turns freely (the filament does not have to rotate on a fixed crosspiece).
* It attached on top of a Taz using zip ties, and is tall enough