The Adaptec ACK-I-rA-HDmSAS-HDmSAS-0.5M is an internal &quot;right angle&quot; 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.