Bottle cage

A bottle cage is device 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, behind the saddle, or, in uncommon cases, the fork. Most modern bicycles have threaded holes in the frame to hold the bottle cage, often called braze-ons even though they may be welded, glued, riveted, or moulded into the frame material. Clamps are necessary on bicycles not so equipped, such as older or less expensive models.

The most common location for a frame-mounted bottle cage is on the top side of the downtube. The most common location for a second frame-mounted bottle cage is on the front side of the seat tube. Small bikes and mountain bikes with rear suspension often do not have enough room for two bottle cages inside the main frame triangle. Some mountain bikes have highly sloped top tubes that limit the size of bottles mounted inside the triangle.

Some touring bicycles have a third frame mounting location: under the downtube.

Bottle cages may be mounted behind the seat with a bracket that attaches to the seatpost.

Some uncommon forks include bottle cage mounts.

Tandem bicycles may have as many as six bottle cages.

Recumbent bicycles may have bottle cages mounted to the steering mechanism or behind the seat back.

The vast majority of bottle cages consist of a single hoop of metal tubing or rod bent to hold the bottle snugly and engage the top, or an indentation in the case of larger bottles, to prevent it from bouncing out.

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Wikipedia