This is an easy assemble pneumatic connector/coupler kit for the 3D printer PTFE tube. This kit includes PC4-01 and KJH04-M6 connectors with buckle clips. These parts will fit any hot end and extruder that uses a Bowden tube for 1.75 mm filaments. It passes through Bowden fitting. Pneumatic connectors give you a quick fitting and secure connection between the PTFE tube and hot end at one end, and extruder at the other end.