iPerfect(TM) 5Pcs Barrel M6 X 30 Teflon Nozzle Throat for MK8 Tube Makerbot 3D Printer Extruder Hot End This is a barrel for both single and dual MK8 extruder with a PTFE tube inside. Please note that the 1.75mm MK8 extruder is not compatible with the 3mm one, and you can not convert your 1.75mm extruder into a 3mm one by just changing the barrel. please confirm your expected diameter before placing the order. Material: Stainless Steel Inner diameter: 2mm for 1.75mm filament Screw thread:M6