Game Boy Advance Game Link Cable

The third generation started with the release of the Game Boy Advance which was released alongside its own link cable called the Game Boy Advance Game Link Cable (model AGB-005) It features yet another new type of link cable port which is used on the Game Boy Advance, Game Boy Advance SP and Game Boy Player. This link cable can only be used for connecting Game Link compatible Game Boy Advance games. The cable also features a link cable 'hub' in the middle allowing the use of up to two additional link cables to connect up to four players at once, in this configuration the plugs are designed so as to be only inserted into the hub in one way due to the plug shapes.

Source: Wikipedia, "Game Link Cable", available under the CC-BY-SA License.