Legris 4mm Tube OD x 1/8 BSPT Brass Compression Tube Male Connector Comp x MBSPT Ends, 300 Max psi, -40 to 210°F 0105 04 10 - 03751138 - Penn Tool Co., Inc
4mm OD 2.9mm ID Compression Sleeve Ferrules and Insert Tube Support 20 Pcs Brass | eBay
20Pcs/Lot 3mm 4mm 5mm 6mm 6.35mm 8mm 10mm 12mm 14mm 16mm ID Brass Fit Compression Sleeve Fitting Sleeve Ferrule Ring - AliExpress
Compression Tube Fitting 4mm x 6mm OD Tube Double Ferrule Coupling Connector | eBay
4mm & G1/8'' Brass T-Shape Tee Compression Fitting with Male Threads 150 bar Zinc plated Steel, with NBR insert DIN EN 1254-2 | Tameson.com
Fitting Metric M10X1.0 Male to Compression 4mm OD Tube Brass
Brass Fitting Metric M6 M6x1.0 Male to Compression 4mm OD Metal or Nylon Tube Elbow 90 Degree
Pipe Fitting M5x0.8/M6x1.0/M8x1.25 Male Fit for Tube O/D 4mm/6mm Nickel Plated Brass Air Compression Union Fitting Adapter Straight Connector - (Size: M8/Thread: Fit for Tube OD 4mm) - Amazon.com