The BlueSpot Step Drill is manufactured from high steel for increased durability and cutting power. Titanium coated to reduce friction and heat. Specially designed for precision drilling of holes in aluminium, brass, copper, plastic, steel and wood. 2mm step increments. The set is supplied in a robust metal case and contains the following: 1 x 5 Step Drill 4-12mm 1 x 9 Step Drill 4-22mm 1 x 10 Step Drill 4-32mm