Home » headsets » Tapered Headsets » m40 TAPERED HEADSETS M40 IS42/28.6 | IS52/40 Alloy Sealed Bearings 1-1/8″ to 1.5″ Tapered Steerer Top Nut: 1-1/8″ Bearing O.D.: 41.8/52 Crown Cone: 39.8 Height: 10 Technical Diagram