These diamond tipped drill bits are especially suitable for working on extremely hard porcelain or marble, and are ideal for drilling into wall or floor tiles. Each bit is filled with an internal cooling gel reservoir which helps to guarantee a longer service life and continuous performance, while also meaning that no additional coolant is needed whilst drilling. The super thin turbo cutting edge ensures an excellent cutting speed and generates less dust, especially when working in the hardest porcelain stoneware. The standard 1/4" hex shank means these drill bits can be used in a wide variety of power tools. A high contact pressure in first gear and a maximum speed of 400 rpm are recommended to achieve best results. It is also advisable to use the tool at an angle when drilling in order to achieve precise positioning without slipping. If your drill has an impact or hammer mode it should be switched off. Features and Benefits • Metric tile drill bit set with four sizes (5mm, 6mm, 8mm,