If you have an older drive or other device that only includes the "four pin" power input (such as a PATA/IDE model), but your computer's power supply only has the newer "SATA" type power connection, this adaptor is what you need.
Plug the SATA connector into the power supply output and the other (4-pin) end into your drive.
Adaptor has male SATA connector and female 4-pin connector.
(Not to be confused with the opposite adaptor which allows older type 4-pin power connections to be used with newer SATA-only drives.)
Number of items contained within a single pack.