Brass is the most popular material for manufacturing coaxial connectors and adapters because of its combination of physical and electrical properties, along with its low cost and widespread availability.
Brass is a relatively easy material to machine and fabricate, which makes it an ideal choice for producing connectors and adapters that require precise tolerances and intricate shapes. This is important because coaxial connectors and adapters must maintain close dimensional tolerances in order to ensure proper electrical performance.
Brass also has excellent electrical conductivity which is critical for RF components. These components are used to transfer high-frequency signals, and the material must be able to conduct these signals without introducing any significant electrical losses or distortions. Brass has a low resistance to electrical flow, which helps to minimise insertion and return losses, and ensure clear signal transmission.
Perhaps one of the most important considerations, compared to materials with similar electrical properties brass is a relatively inexpensive material compared to other metals, which makes it an attractive choice for general purpose applications.