5/16" Armeg PTC Carbide Porcelain Drill Bit 8.0mm - 5/16" PTC Drill CTCP8.0 Easy Start up and rapid penetration in Porcelain tile. Special carbide tip ensures accurate holes and virtually eliminates drill bit wander. Max operating speed, is between 700 and 900 Rpm. Spray water on the PTC bit when drilling, to keep the bit cool and sharp.