This is a 6 Inch 4-Pin to 3-Pin Multi-Fan Adapter. If you in need to power some 3-pin fans from a 4-pin power cable (molex PSU cable), this 4-pin to 3-pin fan adapter will do the trick. This adapter is handy if you don't have enough 3-pin fan power outlets on your motherboard, or don't wish to power your 3-pin fans through your motherboard (for custom fan speed monitoring).