These Hole Saw Arbor Extension are a 22 inch Long (2 piece bolt together) Extension Bit with 7/16" Hex each End (Some people call them 1/2" they are not quite 1/2 in but its the same thing for the sake of Hole Saw Arbors etc. they all fit 1/2 in or 7/16 ) Hex Male to 7/16" Hex Female. Use with 7/16" (11mm) Hex Arbor for Holesaws to Drill Deep Holes in Concrete Brick and Wood etc. Hex Key Included to Lock Hole Saw Arbors in place. 12 inch Hexagonal Extension Fits Any 7/16" or 1/2 in Hex Shaft Hole Saw Arbor - Hex Screw Secures and Tightens Hex Shaft of Arbor or 7/16" 1/2 in Drill Attachment. Use Arbor Extension Bit with our Tungsten Carbide Grit Edge Hole saws To Drill Deep Holes in Concrete Masonry And Brick Walls with TCT Pilot Drills. Note 3/8 inch Hex Also available so make sure you measure and order the correct size for your hole saw Arbor 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 Deep Holes through Studs and Walls for electrical wires and conduit.