What size of compression fitting do I need?

It is important to understand the difference between

Aqua-Dynamic Supply Fitting 1/2 Inch Compression Straight Chrome

Copper Tube Size LF Brass Compression Coupling with Stop

Regusol Compression fitting for copper and precision steel pipe

The Basics of Compression Fittings - Beswick Engineering

Power Steering Lines, Compression Fittings, and Pressure Ratings

Brass Compression Nut, 1/4 Tube Size

40 mm Compression Waste, Waste Pipe & Fittings

What size of compression fitting do I need?

Compression Fittings • MicroGroup