The eSATA Extender Cable from Newer Technology allows you to use up to two extra SATA ports found on your Mac Pro's logic board. This extension cable is engineered to route accurately and properly inside your Mac Pro case. When using it, you'll be able to run up to two external eSATA devices and expand your hard drive configuration to up to 6 hard drives.
eSATA extender cable for Mac Pro 12-Core, 8-Core, Quad-Core
Enables connection of up to two (2) SATA-I or SATA-II devices
Engineered for proper and accurate routing inside case