For further strength and performance, this variable pitch hole saw set is made of heavy-duty steel that contains 8% cobalt. Appropriate for drilling holes in plastic, wood, cast iron, brass, bronze, steel, and aluminium. Maximum cutting depth 38mm. Diameters of the hole saws are 20, 22, 29, 35, 38, 44, 51, 57, and 64 mm. The kit comes with 4mm hex key and 14-30mm and 32-152mm hex arbours. Supplied inside a blow moulded plastic storage case.