Shank taper accuracy AT3 or better. Made of alloy forged steel for long, durable service life. Hardened to RC 52-56 and ground to ensure maximum accuracy. Face is held perpendicular to centerline within 0.0002". Designed for slitting saws up to 5/16" thick. For wider cutters use Stub Arbor Holder. Pilot diameter is sized for precision fit with cutter and is keyed for positive drive. Semi-flush nose cap gets in tight areas. Retention Knobs are sold separately.