Specially ground, single-flute, solid carbide drills ideally suited for use by the professional gun trade on hard receivers (as the 03A3 and harder). Cuts a clean chip in hardest file steel, giving true hole. Does not "crumble out" the steel; thus, no chatter. 2" long to give quill clearance when using with Forster and other scope/sight mounting jigs. Kept properly cleaned, will not bind or break. Properly fed, won't work-harden hole surface like spade drill does; decreases tap breakage. Drills "all the way through" hardened steels. Note: Common sense must be used. No guarantee against breakage! Use only to crack the skin Mfg: Brownells SPECS: Sizes available: No. 33 (6-40), No. 31 (6-48), No. 29 (8-32), No. 28 (8-40). Speed approximately twice that of high speed steel, feed rate the same or slightly less.