I wanted a filament guide that would secure the filament with my spools positioned behind the printer using smaller bearings to eliminate drag and wear. I used these bearings:
Print with 0.20mm or higher layers, with supports enabled. I've tested using PETG and PLA and it's holding up well to use. The pin for the swivel cap is a bit fragile, but should hold well once inserted. You might want to use PETG or warm it up a bit before inserting the pin into the swivel cap at top.
Updated 20190303: V2 files with improved extruder housing clearance at maximum Z and lower bearing axle reshaped to make insertion easier.
Updated 20190304: Added V3 fame clip with improved clearance at maximum Z. This iteration secures well while still clearing the extruder better than the Prusa filament spool holder.
Any PLA, PETG
Prints with very tight tolerances. Apply pressure with pliers as necessary to snap bearings and cover into place.