As much as I hate to say it, I need to start with saying that I can't recommend you stay away from this product strongly enough!
The way this is designed over time the gear will slowly bite into and grind away at the aluminum housing, which creates metallic dust that gets all over inside of the toolhead. Eventually the wear will reach a point that it will cause irregular filament extrusion and impact print quality to a varying degree.
I went through two of these (bought direct from Biqu, before West3D carried them) before I finally realized what was happening and found other posts online of people experience the same issue.
The stock gears are fine, just stick with those and replace them if needed. The plastic gear doesn't come into contact with the filament, so wear on it is minimal to none. The part that comes into contact with the filament is still metal on the stock gears.
