Speedfil F2 Aero Bottle System Stay hydrated with the patent pending SpeedfilTM F2 system. The F2 works with any Specialized thread compatible water bottle in both 21 and 24 ounce sizes. The F2 model enjoys many of the same benefits as our standard Speedfil. The dual splash resistant design allows the rider to refill the system on the fly. Just prime the Speedfil system once and you have access to your hydration immediately. The bite valve and tubing keep fluid on demand without sucking up air for each drink. The F2 works with any standard cage mounted on the down tube. This also allows for simple mounting and cleaning. The F2 can be used by triathletes, mountain bikers, as well as recreational riders. The F2 is the utility player of the Speedfil family.