no waterbottle at all. The most drag was 2 water bottles; one on the down tube and one on the seat tube. A number of products have been created to satisfy triathlete's demands for aerodynamic hydration systems. Examples include the Aerodrink system by Profile Design, an aero bottle that hangs from the handlebars with a straw so the athlete can drink without using his hands; and the Neverreach system, a teardrop-shaped reservoir mounted behind the seat with a tube running up to the handlebars. In addition, certain high-end triathlon bicycles have a hydration system integrated into the frame's tubing itself. On long-distance triathlons, the participants will get filled bottles by the organiser during the race as replacement for the used ones. If using special bottles, the received bottle should be emptied into own bottle, and immediately thrown. Bottles hanging from the handlebars are generally prepared for this. To throw bottles outside aid stations is not allowed. In Ironman own aid suppliers are not allowed. Wheels A vast array of low-weight and/or aerodynamic wheels exist for racing bicycles. Some (such as wheels with an aerodynamic ring, flat spokes, and fewer spokes than the traditional 32) are legal for use in most cycling events, while others such as carbon-fiber tri-spokes (wheels with only three large, rigid spokes) generally are only legal in triathlons and time-trials. Typically wheels that are lighter are preferred and, although this is an obvious consideration, it is not the only one. Higher profile wheels (larger rim) are conducive to laminar flow of air past them more so than traditional thin rimmed wheels. Solid disc wheels are used as well, though in outdoor settings these are generally not used on the front wheel because they are difficult to handle in crosswinds. Disc wheels provide a significant aerodynamic advantage when mounted on the rear wheel improving laminar flow over the rear half of the bike. Recent developments in technology have given rise to disc wheels with a dimpled surface like a golf ball, also in the name of aerodynamics. Disc wheels are not permitted at the Ironman World Championships in Kona Hawaii, as large crosswinds are not uncommon and present an unsafe situation to athletes. Some triathlon bikes use 650c wheels (a nominal diameter of 65 centimeters) rather than the conventional 700c wheels used on nearly all road bikes. The smaller wheels weigh less, have a smaller cross-sectional area (reducing