The 42Piece. Rubber Insulated Clamp Assortment is made of corrosion and rust resistant zinc plated steel with black rubber linings. The rubber lining absorbs vibrations and jolts, reducing wear and tear on cables and hoses. The mounting hole is 1/4-InchD and the sizes included are 1/4-Inch, 3/8-Inch, 5/8-Inch, 5/16-Inch, 1/2-Inch. 42Piece GRIP Rubber Insulated Clamps Assortment Set 1/4-Inch 5/16-Inch 3/8-Inch 1/2-Inch 5/8-Inch 43115