Thanks for your question about your Ballistix memory modules. The two part numbers have the same identical base part (BLT8G4D30AETA), and the difference between the K16FE and K16FD are only build/revision differences. The JEDEC programming in the SPD of the modules may slightly vary, or report differently with third-party programs like AIDA64, which is why one is listed as 2133 and the other is 2400. However, both of these modules will support up to 3000MT/s, pending the system BIOS is configured appropriately to run at that speed. Hopefully this answers your question and clears up any confusion regarding the two different builds!