we have drill bit for Dia 8mm,10mm,12mm,14mm,16mm,32mm,38mm,40mm,44mm,etc
it designs two -gear rotary speed,you can turn the knob to adjust its speed,high gear is suitable for the diamond drill bit of 20-52 diameters,it is also equipped with safety friction clutch,it is easy,safe and reliablke to ues.