This is my quick, simple and cheap filament holder I designed a while ago! Seeing as I've had faultless performance from it so far, I thought I'd share it!
It uses 4 standard size (22mm outer dia., 7mm thickness, 8mm center hole) skateboard bearings, which can be purchased very cheaply from Ebay, or as in my case, salvaged from an old and dead skateboard that was destined for the bin! The bearings should be a tight fit into the rollers, but once in, won't require any glue. These bearings allow near faultless and very smooth rotation of your filament spool.
The bolts I used to attach the rollers to the bases are M8 x 30mm, but slightly shorter ones could also be used and any size bolts can be used for connecting the 2 bases together (holes may require drilling if any larger than M5), as this just makes the whole unit more solid, while still being adjustable to fit any size filament spool.
If like me, you have a slippery desk surface, you may want to put some adhesive rubber feet on the bases like I did as this will ensure that the holder doesn't move while printing.
Any feedback is welcome. Thanks :)
EDIT: I updated the Base.stl file as I realised that I uploaded an old version by accident. The 2 5mm holes for the 2 long joining bolts were too close to the rollers and may have caused fitment issues. All fixed now :)