Pneumatic Air Quick Connector Fitting Pipe 1/8" NPT to 4mm ID 6mm OD Tube @F3 | eBay
Amazon.com: uxcell Air Pneumatic Tube 4mm Push in Connector Fittings 5 Pcs : Industrial & Scientific
Amazon.com: 4mm OD Push to Connect Fitting Push in Connector 1/4 NPT Male Air Fittings Pneumatic Fitting,CEKER 4MM Air Tube Fittings Air Line Fittings Quick Connect Air Hose Fittings for 3D Printer
4mm Plastic Pagoda Barbed Equal Elbow L Type Hose Connector Pipe Fitting Tube Joint for Garden: Amazon.com: Industrial & Scientific
4mm x 1/8'' NPT Push-in Fitting with Male Threads Stainless Steel FKM | Tameson.com