ICS3 (Internal Cable Stops) erradicates the need to run internal cable housing the entire length of the tube, which adds friction and up to 200 grams of dead weight.

Internal Cable Stops on the other hand, function much like external stops. The housing fits into the stops and the bare cables travel in unobstructed paths through the frame, into the bottom bracket cable guide, and straight to the derailleurs.

ICS3 also reduces aerodynamic drag by placing the cable housing entry out of the wind behind the stem. In order to have the cables enter the top tube, yet travel unobstructed through the downtube, Cervelo's ICS3 frames use Teflon-lined stainless steel tubes, curved to guide the cables into perfect alignment with the Bottom Bracket cable guide.

A simple method to reduce aerodynamic drag is to remove or hide objects from the wind. In some cases a brake can be completely integrated into the frame structure as if it doesn’t exist at all. However, in other cases, there are practical limitations to this level of integration. One of the real world constraints of a road bike is that riders and mechanics need to have quick, easy access to most parts on the bike. Under these conditions, complete rear brake integration is problematic for road racing. An effective and practical solution is to position and shape the seatstays to hide the rear brake from the wind.  

Dropping the down tube “hides” it in dirty air, reducing the high pressure normally found on the down tube’s leading edge, and eliminating the low pressure air that normally pulls rearward on the fork crown.

Frames are but one component of an entire system. Cervelo considers your hydration needs as part of the aerodynamic equation. Two water bottles fit in the usual positions: one on the seat tube, one on the down tube. In the standard 2-bottle arrangement, the bottles fit together tightly with each other and the frame, reducing the gaps where turbulence can form for lower aerodynamic drag.

In addition, an extra bottle boss on the down tube creates a new lower position for a single bottle. Using the low position on the down tube saves 14 grams of aero drag, a reduction of about 1.4 watts, compared to a bottle in the usual position.