Master Mechanic, 12, Hole Saw Extension, 38 Hex Shank Extension Fits Master Mechanic White 1 Piece Bi Metal Hole Saws Mandrels, Also Designed To Fit Any 38 Round Or Hex Shank Tool, The 12 Length Is For Drilling Deep Holes Or For Hard To Reach Areas, Flats On The Shank Provide Positive Driving Action