Cane Creek 40-Series ZeroStack Conversion Bottom for 49mm Head Tube 1-1/8" Crown Race Diameter 40-Series Represents the Perfect Balance of Performance, Durability and Value Tops and Bottoms Sold Separately As Part of Cane Creek's Tapered Headset Solution Internally Contoured 6061-T6 Aluminum Cup Sealed Black Oxide Steel Cartridge Bearing Durable Steel Crown Race with Low-Friction Face-Seals Consistent Stack Heights Across 10, 40 and 110 Series Internal Parts Are Cross-Compatible Across 10, 40 and 110 series