This is filament guide for flexible filaments designed for use with a particular setup:
Monoprice MP Select Mini, OEM extruder gear (read: cast and chromed, with the groove on the gear instead of the bearing) kept in lieu of the Anycubic-provided aftermarket version (read: machined brass with flat sides).
Anycubic Mk8 extruder (right hand), w/the Anycubic-provided grooved idler bearing substituted with a plain, non-grooved 4x10x4mm miniature bearing.
Requires slightly longer M3 bolts. 25mm does the trick.
This was printed with PETG, but I suspect it would work fine printed with most types of relatively-rigid materials (eg. ABS, PLA).