Features: Blair 11,000-SERIES or 13,000-SERIES ROTABROACH CUTTERS... for heavy duty use in sheet metal & materials up to 1/2 thick. Annular tools that cut clean, burr-free, and round holes fast... unlike twist drills that push or hole saws that tear thru materials. Because they're hollow, there's no dead zone as with a twist drill, so less thrust is required and no deforming of stock or jagged edges occurs. Multiple cutting teeth, precision ground instead of stamped like hole saws, give long tool life. For body shops and frame straighteners, custom building and detailing, aftermarket and trailer hitch installations, rustproofers and undercoaters... wherever fast, rugged, and superior quality holes are required... Rotabroach 11,000-Series Cutters are the single answer. Patented tooth geometry also prevents chip clogging when cutting steel, sheet metal, plastic and wood. Arbors for 11,000-Series cutters fit 3/8 and 1/2 hand held drill chucks and use a spring loaded pilot guide or skip-proof pilots to eliminate pre-drilling operations. -Fits 3/8” or 1/2” Chuck - Rugged Arbor Houses Pilot Guides and Adjustable Tension Spring-Patented Long-Lasting Tooth Design-Spring-Loaded Heavy Duty Pilot-Guide Eliminates Pre-drillingCan Be Used For:-Drilling Slots-Groove to Depth-Tube Joints-Partial holes-Removing bolt, screw, and rivet heads-Removing frozen nuts-Fractional Sizes ¼” thru ¾” sizes sold in packages of 3-Dia. (inches)---5/16-Decimal equiv. (inches)---.3125-Max D.O.C.—1/4