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
Made in USA - Compression Tube Connector: 1/2 & 1/2-20″ Thread, 1/2″ Tube OD, Compression x Threaded - 32874620 - MSC Industrial Supply
Stainless Steel Compression Fitting Male Connectors - 3/8"T x 3/8"NPT
Ideal Vacuum | Swagelok Tube Fitting, ¼ MNPT to ¼ Tubing Male Connector, Gaugeable, Monel Alloy 400/R-405, PN: M-400-1-4
Straight Push Connectors 6mm to 4mm Quick Release Pneumatic Connector Plastic Union Tube Fitting Grey 5Pcs - Walmart.com