CMD5122420 16 piece Masonry Twist Drill Bit Set, 4mm to 22mm. The 16 piece set of masonry drill bits from RS PRO features drill bits in sizes ranging from 4mm to 22mm that are ideal for use in a wide range of electrical installation and maintenance work. These high quality drill bits are compatible with power tools such as hammer action drills, ensuring quick and efficient drilling in a variety of masonry materials such as concrete and brick. The RS PRO 16 piece masonry drill bit set is supplied with a durable storage tool roll case with easy access, ensuring the bits are organised and protected when not in use.