Before revision: How they work In small sizes, the compression fitting is composed of an outer compression nut and an inner compression ring or ferrule ( sometimes referred to as an "olive") that is typically made of brass or copper or steel.
After revision: How they work In small sizes, the compression fitting is composed of an outer compression nut and an inner compression ring or ferrule ( in the UK referred to as an "olive") that is typically made of brass or copper or steel.