The Adaptec ACK-I-HDmSAS-4SAS-SB-.8M is an internal Mini Serial Attached SCSI HD x4 (SFF-8643) to (4) x1 Serial Attached SCSI (adapter based) fan-out cable with sideband signals (SFF-8482). It measures 0.8 meters and is used for connecting a SAS/SATA adapter to to SAS disks, or a SAS/SATA backplane.