Spool Holder / Marble Machine

What is more fun than a spool holder and more useful than a marble machine? A spool holder/marble machine! This extruder-driven marble machine uses 6mm airsoft pellets as recirculating bearing balls for a friction-free spool holder. When you get tired of watching your printer print, you can now keep yourself entertained by watching your filament spool turn! Designed for 8" diameter (nominal) spools, 3 1/4" wide or less.New: I've just added a "slim" version that is more stylish and use a little l