Summary An easier and safer way to pull back the idler bar springs - keeps the thumb and fingers further away from the drive gear - although you probably shouldn't be messing with the idler bar springs while the gears are actively turning... For use on extruders with idler bar spring assemblies that modify filament feed tension. Prints upright w/o support; Currently used with a Fusion3 F306 3D printer to help change out filament type/color a little quicker.