The Bowden principle: The Bowden cable lets you reduce the moving mass of the extruder and thus allowing faster controlled motion less shaking of your machine less energy use and importantly faster printing! Normally the mechanism that drives the filament into the hot end (where it melts) is directly on top of the extruder. This creates problems of balance and oscillations with faster motion which you can see in your printing results and hear and feel when your machine is shaking. If the filament drive mechanism is placed on a non-moving part of the 3D printer it can be pushed into a tube. PTFE (Teflon) is useful because it is slippery: it has little friction with the plastic.This limits wear and loss of energy. The tube's other end is connected to the extruder's hot-end. The concept of using a Bowden cable as guide was suggested and pioneered by Ed Sells. The main advantages: All metal enables working with Polycarbonate up to 300 degrees Celsius and with future materials that require higher working temperatures beyond those supported by plastic extruders and hot end. Tested with PLA ABS polycarbonate nylon and PVA. Features: It is assembled with 4.7ohm 8W resistor and 100K NTC thermistor. To make your printing easier a 30 x 30mm 12V DC cooler fan is assembled for heat dissipation; Nozzle Size: 0.4mm; Filament size: 1.75mm