The filament guide of the UM2 is far from optimal. After some hundreds hour of work it shows signs of tear and wear and as you might see from the first picture the filament grinds large traces into the guide. Finally this leads to frequent filament ruptures which results in wasted printing time and unhappy users.There a still some improved filament guides but I designed my own because I wanted something with a ball bearing which let your filament run very smoothly.1. So print one base, two wheels and the axle. 2. Then insert the ball bearing inside the two wheels and glue the two wheels together (I used epoxy to do this but I thing any decent glue will do.)3. Screw all parts together with the M3 bolt, nut and washer4. Replace the original guide with your new one.5. Face no more broken filaments :-)