The first generation used the V300 Toshiba 19nm Toggle-Mode 2.0 NAND Kingston but was replaced by Micron 20nm asynchronous NAND without notifying. The difference between the two is huge !! The Toshiba NAND has a maximum speed of 200 MB / s, while it is only 50 MB / s for the Micron NAND. The product with the 505/520 firmware work fine. But if you have the product with the 506/521 firmware suddenly I assure you of 50MB / s .... I who bought the Kingston eyes closed ... so I took a sandisk SSD and there no worries the speeds are waiting for you