Dia-Compe have for some time been part of the Cane Creek component empire, but back in the day they were the originators of the Aheadset, which is almost a selling point by itself.
Rather than using a solid crown race like most other manufacturers, Dia-Compe put a split in theirs so that it can be slipped on and off without special tools. This headset uses steel rather than stainless steel angular contact cartridge bearings, giving a finite lifespan, but the seals have been shown to provide ample protection for road bike applications. Also available in a gold finish. It’s available in 1 1/8in only.