Convenient Unibits allow multiple hole sizes without the hassle of changing drill bits. HSS titanium coating makes them perfect for drilling into plastic, steel, copper, wood, aluminum, and many others. Convenient Unibits allow multiple hole sizes without the hassle of changing drill bits. HSS titanium coating makes them perfect for drilling into plastic, steel, copper, wood, aluminum, and many other materials. With 10 total steps which range from 1/4" Through 1 3/8" this bit is particularly useful when installing ebb&flow systems or making your own hydroponic drip systems.