Hardware.Info posted Western Digital Caviar Black V2 4TB (WD4003FZEX) review: faster Black hard drive
A quote from the article:
In late October, Western Digital released a new version of its Caviar Black Edition hard disks. WD calls the new ones 'Caviar Black' like the original series, but promises better performance compared to the first version. We tested the 4TB model.Western Digital Caviar Black V2 4TB (WD4003FZEX) review: faster Black hard drive @ Hardware.Info
While WD called the new version by the same name, it does have new product codes. For example, the original Caviar Black 4TB was called the WD4001FAEX and the new one WD4003FZEX.