Even though this wheel comes with a full-blown Power Tap 2.4 wireless powermeter in the hub, it still offers all the aerodynamics of the standard 900 disc. It has only 19mm of frontal area, so it's nearly invisible to the wind. It has a dimpling pattern unique to the 900, which helps smooth the air flow to minimize drag. Its Aerodynamic Boundary Layer Control (ABLC) carbon fiber skins are embossed with over 4900 golf ball-like dimples in 5 different sizes patterned to force the airflow to form less turbulent boundary layers. You get less drag in all wind angles, as well as less buffeting of the disc in crosswinds.

According to Zipp's testing, the 900 disc is laterally stiffer than the Sub-9. And, amazingly enough, it's $200 less costly than the Sub-9 version. While the Sub-9 offers superior aerodynamics and vertical compliance, the 900 disc is hardly a compromise.

The 900 Clincher Disc/Power Tap 2.4 is available in 700c only; it comes in your choice of Shimano/SRAM or Campagnolo. Since Zipp manufactures the hub itself, you can upgrade it to ceramic bearings. The disc comes with an angled valve adapter so that the tire can be pumped up and six Zipp "jersey" patches for covering the valve cutout. The disc comes complete with Power Tuned Agent 7.0 Software which is Mac and PC compatible, computer head and harness and the USB interface so you can download the data from your handlebar-mounted computer to your desktop.