Professional Quality 7/8" Diameter Diamond Plated Drill Bit. Our WGS diamond coated drill bits have a knock-out hole in the shank for easy spent plug removal. The heavy and deep layer of diamond coating enables this bit to drill up to 200 holes when used properly. All diamond bits must always be used with suitable diamond coolant applied by spraying or immersing the bit while drilling. For drilling glass, tile and stone. Hole Diameter: 7/8", Shank Diameter: 5/16", Overall Length: 2-1/4"