Hollow Square Drill Bits Hollow Square Drill Bits Product Specifications Chisel Cutting Length Over All Length (mm) 1/4" 40 210 3/8" 60 210 5/16" 60 210 7/16" 75 210 1/2" 75 210 5/8" 90 210 3/4" 90 210 1" 90 210 3/8" 75 210