Hole Diameter: 3/16 in (5 mm) Core Diameter: 1/16 in (1.6 mm) Shank Diameter: 5/16 in (8 mm) Overall Length: 2-1/4 in (57.4 mm) Drilling Depth: 1 in (25.4 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 1/4" 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.