Advantage 1: 12 inch Hole Saw Extension bit extension 12" Long Bit Extension with Double end. Advantage 2: Drill Long Reach Extension for Drill Bits with 3/8”, 7/16" Hexagonal Shaft 12” Extension Drill Bit Heat Treated Hex Drill Extension. Application: 3/8”, 7/16” Double end Hex Extension Drill Extension Bit Holder 3/8”, 7/16" Hex Male to 3/8”, 7/16" Female Hex Shank Extension allows you to Drill Deep Holes for hole saw arbor Package: 1 x 12” extension mandrel bar,1x T-sharp ratchet screw driver 6 x 1” CrV screw driver bits. 3/8”, 7/16” Double end Hex Extension Drill Extension Bit Holder 3/8”, 7/16" Hex Male to 3/8”, 7/16" Female Hex Shank Extension allows you to Drill Deep Holes for hole saw arbor .