Features These collet clamps and clips are designed to eliminate the backlash created by the collet in the embedded bowden couplings.The collet clip should be pushed under the plastic collar to stop any back and forth movement of the PTFE tubing as it is extruded and retracted.This will greatly improve the accuracy of the Specifications: Material: ABS Color: Black; Blue For 4 mm/0.16 in.tubing Package List 20 x Black Collets 20 x Blue Clips Warm Tip Please check the size carefully before purchasing.