Dual Angular Contact,this describes the use of both angular contact bearings and angled bearing cups/hub bores used in the hub design.

The AC-2 hub features revolutionary bearing installation and function never seen before in a bicycle hub. It has been designed from the ground up for ease of maintenance and optimal bearing performance.

Here are a few key points of the AC-2 BMX Front Hub: The AC-2 hubs use 20mm Angular Contact bearings with a wave spring pre-load. Bearings are pressed into tapered cups that mate with the angled bores machined into the hub shell. This design feature allows bearing/cup to be easily installed and removed from hub shell without any special tools. No more presses or hammers needed!

Another attribute of the tapered bearing cup/angled hub shell bore design is how the bearings seat in the hub. The bearings/cups on each side of the hub shell are in perfect alignment with each other! This ensures superior bearing performance and less chance of premature wear.

Hub shell literally floats on the axle. The only force on the bearings is supplied by the wave spring (which delivers the appropriate bearing pre-load needed for angular contact bearings). Tightening of axle bolts has absolutely no affect on the bearings!

The bearings, wave spring, and shim(s) are secured on the axle by one retaining ring. The only tool used to assemble/disassemble the AC-2 hub is a pair of snap ring pliers!