Zipp: Optimized for both side and direct bottle entry the Alumina cage provides easy access to hydration, especially on smaller frames and those with tight angles. Thin-but-strong arms flex for easy bottle insertion and removal, at any angle. Worry free hydration when speed matters.The new Alumina aluminum cage shares the same innovative sleek design as the carbon SLSpeed cage and challenges any titanium cage costing twice as much.Alumina cages are both designed for seat tube or down tube mounting on road, cyclocross and mtb frames.