The Diamondhead USA (Turbo Core bit) 

Diamondhead USA Continuous Turbo Gray Core Bit with Shaft can be used on all types of porcelain and ceramic tiles either dry or wet. They are able to withsatnd the toughest working conditions and are widely used in the North American market. They are available in sizes 1/4" to 3" with a 10 mm shaft of 5/8-11. In a case of 10.