what is the difference for “1.75-0.4mm” and “4.1mm bore (upgraded)”
The difference between these two models is the inner hole of the throat, see the drawings below .
How to choose which size to buy?
If your printing temperature is within 0°C-220°C, then choose “4.1mm bore (upgraded)”, In this way, there will be no blocking situation.
If your printing temperature is within 260°C-300°C, then choose “1.75-0.4mm”