This kit comprises two separate 500GB internal hard disk drives. One drive replaces the MacBook Pro's regular internal drive. The other is part of a kit that resides in the "SuperDrive" bay, replacing the internal optical drive. The kit also includes a slim, portable enclosure that turns that optical drive into a USB 2.0-based SuperDrive instead.
The two drives offer matched performance--both are 2.5-inch disk drives operating at 5400RPM. Apple's own Disk Utility software is used to manage the drives, so you can initialize and partition them as you want; you can configure them either as a two-disk RAID array or operate them as separate volumes. With Leopard, you could also use one drive as a Time Machine backup of the other.
This story, "MCE Offers 1TB Storage for 17-inch MacBook Pro" was originally published by Macworld.