I assume you are referring the Corsair Neutron GTX SATA 3 6Gb/s solid state drive.
If you look at the model numbers you will see they are slightly different.
Model #: CSSD-N120GBGTX-BK and Item #: N82E16820233342
Model #: CSSD-N120GBGTXB-BK and Item #: N82E16820233404
The second one is newer. I also noticed the synthetic benchmarks are slightly different. The newer ssd probably has the latest firmware update.