Double-end end mills have cutting edges on both their ends that remove material from the surface of a piece of stock. They are used on CNC or manual milling machines to create parts with complex shapes and features such as slots, pockets, and grooves. Double-end end mills can accomplish more milling tasks than single-end end mills before they need to be replaced. When the cutting edges on one end wear down, the tool can be flipped over to expose the fresh cutting edges on the other end. Flutes on the end mills' cutting heads carry the removed material away from the workpiece to prevent damage to the end mills or workpiece.