Double ferrule tube fittings are the most common style of instrumentation fittings, and they can also be purchased in brass materials.
Brennan Industries, N2650-04-04-04-04-SS
Stainless Steel Brennan for Structure Pipe, Size: 2 inch at Rs 80
Brennan Industries N2406-B Double Ferrule Tube Fittings - Brass
1/4 Tube O.D. Union Elbow, Double-Ferrule Stainless Steel - Hi
How to Assemble the Hyferset for Two Double Ferrule Compression
Brennan Industries N7202 Double Ferrule Tube Fittings
Brennan Industries N2405 Double Ferrule Tube Fittings
Double Ferrule Tube Fittings at Brennan Industries
316 Stainless Steel, Compression x MNPT, Male NPT 90° Elbow