bearing supported spool cradle with filament guide (fits Wanhao i3 built-in bolt holes)

This is a ball bearing supported filament spool holder that is compact, can mount using the Wanhao i3 frame spool bolt holes, and has a built-in filament guide. The filament guide is a captive ball joint that will fit 4mm diameter teflon tubing. I haven't yet developed a good solution for capturing the bottom end of the filament guide tube at the extruder, so for now I'm using a short length of teflon tube held only at the guide end in order to keep control of the filament as it leaves the spool