Connectors

Here's a few common connectors found on computer fans. They are categorized by pitch, and of course, the number of circuits. Pitch is the distance between the header pins that the connector plugs into. The yellow line in Example A in the photo below shows the pitch measurement.

Computer Fan Connectors

2.0mm Pitch Connector E) 2.0mm (.079") pitch 2-pin connector. These are very popular in many industries. In computers, they're often found on video card fans, particularly ATi.
2.50mm Pitch Connector D) JST 2.50mm (.098") pitch 2-pin connector. The barbed friction ramp make this a very distinctive design. These are very popular in many industries. In computers, they're often found on video card fans, particularly nVidia.
2-pin 2.54mm Pitch Connector C) standard 2.54mm (.100") pitch 2-pin connector.
3-pin 2.54mm Pitch Connector B) standard 2.54mm (.100") pitch 3-pin connector.
4-pin 2.54mm Pitch PWM Connector A) standard 2.54mm (.100") pitch 4-pin connector. For PWM fans.
4-pin 2.54mm Pitch SL Connector 2.54mm (.100") pitch 4-pin SL connector. Typically used for audio cables and some fans, such as Dell.
3.96mm Pitch Connector 3.96mm (.156") pitch 2-pin connector. These connectors sometimes show up in PC's; mostly in power supplies.
5.08mm Pitch Molex Connectors Molex 5.08mm (.200") pitch power connector, Male and Female Pass-Through.
5.08mm Pitch MolexDuo Connector Molex Duo 5.08mm (.200") pitch power connector, Male and Female connectors are combined into a single crimp housing. Provides the same functionality as standard molex power connector but saves space and reduces clutter. They tend to be more fragile and don't fit as well as standard molex power connectors.