⌀ 3 & 4 mm the drill bits are supplied with a round shank. Tungsten carbide tipped (TCT) drill bits allow drilling into concrete, aerated concrete blocks, masonry, slate and granite. From ⌀ 5 mm the hammer drill bits are supplied with a 3 flat shank to prevent the drill bit slipping in the chuck. Red flute to identify the drill bit easily in the users tool box. Can be used in hammer and rotary mode.