Description:Extruder gear inner bore: 5mm. ( You can change according to the actual situation,for example, use MK7 Bore 5mm gear)Designed for 1.75mm filament,Pipe outer diameter need <4.2mmFeatures:- Symmetrical design (The motor can be installed in the left or right side).- Complete assembled and tested.- All - metal extruder.- Extruder drive is stable and accurate.- Direct drive extruder.- Suitable for 42 stepper motors and precision planetary reducer motor.- Can be driven as short range or remote extruder.- Easy to replace filament , you just need pushing it.- Compatible with E3D / J-head / MK8 etc.