This small easy-to-print device can protect your filament-based 3D printer from two common issues - dust and friction.

A piece of sponge wipes the filament clean from any dust particles and prevents them clogging the extruder.

By dropping a few drops of ordinary household mineral oil on the sponge, the filament passing through gets lubricated, thus relieving the extruder motor from strain.

Lubrication is especially useful if the filament needs to travel through long tubes before it enters the extruder (like in the AMS Lite)

But it also helps to reduce the friction inside the extruder below the drive-wheel, where the filament is in compression on its way down to the hot-end.