This MK7 Drive gear with 5 mm bore is typically used in the BQ Witbox 1 3D printer. Compatible with 1.75 mm filament.
These hobbed pulleys can be used in direct drive filament extruders, but they are also compatible with many other extruder designs.
Mini Hyena Filament Drive Gear
This MK7 Drive gear with 8 mm bore is typically used in direct-drive extruders with geared stepper motors. Compatible with 1.75 mm filament.
MK8 Drive Gear for direct-drive extruder; central bore of 5 mm.