For drilling instructions and tips, please, click here . Hole Diameter: 1-1/4 in (32 mm) Core Diameter: 1-1/8 in (29 mm) Shank Diameter: 3/8 in (10 mm) Overall Length: 2-1/2 in (63.5 mm) Drilling Depth: 1-3/8 in (35 mm) High quality new hi-tech design diamond coated drill bits (plated series) should handle all your glass drilling needs. Heavier and deeper layer of diamond coating and notches in the core allow to drill up to 200 holes in OE" thick flat glass. Diamond drills must always be used at a proper speed with suitable diamond coolant applied by spraying or submerging the contact area. Use of plain water will drastically reduce life of your drill. Diamond Tool Coolant is a Must for All Diamond Drilling. Recommended to use with our CRL Diamond Tool Coolant to prevent overheating and prolong tool life. Use our Retaining Drilling Ring to keep the drilling area constantly submerged under the coolant. To achieve maximum life for your diamond drill you may also need our Sharpening Stone . For drilling instructions and tips, please, click here .