The stock belt path for the Ender 3 Y axis is absolutely horrible. It keeps snagging on the extrusion if it isn't perfectly angled and even then it may snag. This not only reduces the life of the belt, it potentially causes print quality issues.
This set of a Y axis tensioner and a Y motor mount fixes this by adding toothed pulleys to lift the belt up for a more direct path that absolutely clears the extrusion's edges.
**Extra hardware required ** - 3x GT2 idler pulley, 3mm bore, 16OD, 6mm wide belts, 20t - A longer 20t 6mm wide belt(these can be bought in meter rolls on eBay or Amazon) - 3x M3x20(or longer) bolts with locking nuts - 13x M3x10 bolts(no longer) - At least 4x M3 washers to center the pulley at the motor, but these are useful to add to every bolt - 4x M3 T nuts(I use spring nuts, but any T nuts are fine)
**Helpful hint:** Don't get regular bolts, nuts and washers on Amazon. Find a webshop in your country that sells bolts and nuts, you will get many more for way less. In Denmark we have a shop called Skruebissen, I usually get 50 M3 bolts for anywhere between 0.7€ and 3.35€ depending on the length of the bolt, and nuts are also really cheap.