3-8 inch Hole Saw Extension These 3/8 inch Hole Saw Extensions are a 22 inch Extra Long (2 Piece Bolt Together) Extension Bit with 3/8" Hex Male to 3/8" Hex Female. Use with 3/8" (9.5mm) Hex Arbor for Hole saws to Drill Deep Holes in Concrete Brick and Wood Hex Key Included to Lock Arbor in place. Heat Treated 12 inch Hexagonal Extension Fits Any 3/8" Hex Shaft Hole Saw Arbor - Hex Screw Secures and Tightens Hex Shaft of Arbor or 3/8" Drill Attachment. Use Arbor Extension Bit with our Tungsten Carbide Grit Edge Hole saws To Drill Deep Holes in Concrete Masonry And Brick Walls - 7/16 Hex Also available so make sure you measure and order the correct size for your hole saw or drill or there will be wobble with an incorrect fitting hex. Plumbers Tools for Drilling Holes for Pipes to go through walls. and Electricians Tools for Drilling Holes through walls for electrical wires and conduit.