Drill guide is sized for drill bit sizes: 3/8 to 1/2". 9 drill sizes include: 3/8, 25/64, 13/32, 27/64, 7/16, 29/64, 15/32, 31/64, 1/2". Guides are made from special nickel alloyed steel that is heat treated for durability. "V-groove" design allows perpendicular alignment on round and cornered material. V-DrillGuide® features a precision ground base to assure stability and accurate perpendicular alignment of drill bits on flat surfaces. Lifetime Warranty. 100% American made quality. It's like a portable drill press! 1 lbs (0.5Kg) shipping weight.