A KDZ file is the official format LG uses for its stock firmware. Unlike custom ROMs which typically come in ZIP formats, KDZ files are designed to be flashed using specific LG service tools. LG K51 (LM-K500MM). Carrier: Metro by T-Mobile (MPCS).
If your device is stuck in a boot loop or won't start, you can "flash" this file to restore the operating system. Downgrading: k500mm10r-00-mpcs-us-op-0902.kdz
This specific firmware is typically used by power users and technicians for: A KDZ file is the official format LG