The Fenvi HDcaddy replaces your internal SuperDrive with a high performance SATA hard drive caddy for a 2,5” HDD or SSD (Solid State Drive) up to 1 TB. You can replace your normal drive for a faster SSD and have second larger HDD for you data storage. Or just to upgrade your data storage so you don’t have to carry around an extra external drive. The metal body of the optibay fits perfectly in the space of your SuperDrive. It is also possible to buy a portable USB 2.0 enclosure for you SuperDrive that will turn it into a bootable, portable, USB powered external SuperDrive which functions exactly the same as it would in your MacBook.