Adjustable Spool Holder - 608 Bearing Based - With Adjustment Knobs

Yet another spool holder, sure there are other designs out there but I just had to design my own. What sets this one apart? Knobs. No screwdriver required for adjusting the width of the spool. Designed to accommodate the various spool sizes I've encountered so far (Printrbot both 1.1 and 2.2lbs, Seacans, and Filaments.ca).

Utilizes easy to find 608 bearing (skateboard bearings) and about $5 worth of metric nuts and bolts.

Hardware:
Four 608 Skateboard Bearings
Four 20mm M8 Hex Bolts (May use cap style instead)
Four M8 Hex Nuts
Four 20mm M5 Hex Bolts (Must be hex head NOT cap head)
Four M5 split ring washers

Tools:
Hammer for gently encouraging M5 bolts into the printed knobs.
Fingers or needle nose pliers, do not use wrenches as you don't need that much force or you could break your parts.

Printer Settings: These are what I used on my Printrbot Simple Metal
0.4mm Layer Height
15% Honeycomb Infill
2 Perimeters
2 Top/Bottom Layers