A bottle cage is container used to affix a water bottle to a bicycle. Composed of plastic, aluminum, stainless steel, titanium or carbon fiber, it is attached to the main frame of a bicycle, the handlebars, or behind the saddle. Most modern bicycles have threaded holes drilled into the frame to hold the bottle cage. Clamps are necessary on older bicycles. Some examples of bicycle lighting take advantage of the bottle cage by using it to hold a bottle-shaped battery to power the lights. This sort of bicycle lighting has proved popular. Until the 1960s, cyclists often carried a second bottle on the handlebars, held by a bottle cage fixed to the handlebars themselves and by a third point to the handlebar stem. Such bottle cages are familiar from pictures of the Tour de France. Riders had a cage there rather than have two on the frame, where the centre of gravity is lower, because at the time the Tour's rules insisted that riders carry a pump. The pump took up the length of one frame tube and made a second bottle cage on the frame impossible.
