Cane Creek 40 ZS44/28. 6 Top Headset - Short cover This is one-half of a complete headset (the upper portion only). You would pair it with a separate matching lower assembly sized to suit your frame/fork to have a complete headset. Fits upper head tubes built to the Zerostack standard (44mm outer diameter cup) and 1 1/8 threadless steerer tube. Has a stack height of 8mm. Features Durable Made of 6061 T-6 Aluminum Clip-Seal Completely seals the top assembly41mm bearing Dependable zinc coated, sealed bearings | Cane Creek | 40 Zs44/28. 6 Top Headset Short Cover, Zs44/28. 6Mm