Dell 5GPWK is a SATA hard-drive power cable for the ECT1250 Tower. It is identified by Dell as the ELEKTRA MT cable assembly and as the HDD power cable supplied in kit 575-BCSK. The cable provides the power connection for the drive assembly in that tower configuration.
This part number is specific to the tower version: Dell lists 84YD9 for the ECS1250 SFF, so the two cables are distinct. Kit 575-BCSK is listed for the Pro Tower Essential QVT1260 and Tower ECT1250, and includes a caddy bracket, screw, power cable and SATA cable. The standalone 5GPWK listing here identifies the power cable component.