VERSATILE This 20 piece wire brush cleaning kit has a wide range of applications, including removing carbon from internal threads or pipes and cleaning drilled holes. DURABLE: Made from tough steel, brass and nylon, each brush has a 6mm (1/4") hex drive shank. EXTENSION INCLUDED: The kit includes a quick release screwdriver with a comfortable handle and a 150mm (6") extension with a quick release chuck. Contents: Brush material and size: Steel, brass, nylon - 6.35, 9.5, 12.7, 15.9, 19 and 25.4mm.