The ThinkPad 1 TB 5400 rpm SATA 3.0 Gb/s 9.5 mm 4k Hard Drive option is our largest capacity hard drive and provides TB capacity in a smaller form factor. This configuration consists of a two 500 GB platter design providing the largest capacity available in a 2.5-inch drive. The advantage of this design is that it decreases the drive height from 12.5 mm to the current 9.5 mm enabling usage in smaller machine designs providing maximum capacity. The Advance Format or 4k sector emulates the 512 sector drives while delivering higher capacity points along with improved error correction capabilities. In addition to the advanced format, this drive features SATA 3.0Gb/s data transfer capabilities. For additional storage and backup, install the ThinkPad 1TB 5400rpm 9.5mm 4k Hard Drive II using the ThinkPad Serial ATA Hard Drive Bay Adapter III (43N3412).