The Microsemi Adaptec ACK-I-rA-HDmSAS-HDmSAS-.5M is an internal "right angle" Mini Serial Attached SCSI HD x4 (SFF-8643) Mini Serial Attached SCSI HD (SFF-8643) cable. It measures 0.5 meter and is used for connecting a SAS/SATA adapter to a SAS/SATA backplane.