1、6 Specifications: The pack contains 6 kinds of bore brushes with different diameters to meet your different cleaning needs, and there are two of each diameter for replacement. 2、Hex Shank: Each bore cleaning brush has a standard 1/4 inch shank, which can be connected with a hand drill or an electric drill for more efficient cleaning. 3、Ease of Use: Excellent wire brush can thoroughly clean rust and details, and twisted pair design enhances cleaning effect. 4、Premium Material: The shank is made of stainless steel, which is resistant to rust and corrosion and has long term stability in harsh environments. 5、Multiple Applications: The hole brush set is suitable for cleaning and rust removal in home, automobile, manufacturing, machining and grinding applications. Item Type: Bore Brush Set Shank Material: Stainless Steel Size: Brush Length: Approx. 100mm/4in Brush Diameter: Approx. 8mm/0.31in, 10mm/0.39in, 12mm/0.47in, 15mm/0.59in, 17mm/0.67in and 19mm/0.75in (2 pcs each) Hex Shank Size: Approx. 6.3mm / 1/4in Extension Rod Length: Approx. 15cm/5.9in 12 x Bore Brush Set 1 x Extension Rod