* HTC's ROM Update Utilities, better known as RUUs, are all-in-one Windows
programs that install official software versions for HTC phones. The latest one
is the official Android 5.1 update for the flagship One M9 Developer Edition,
allowing an easy path back to stock software. That's especially important for
the Developer Edition, since its unlockable bootloader encourages custom
ROMs
*Download Link.HERE
RUU_HIMA_UL_L51_SENSE70_ATT_MR_NA_Gen_Unlock_2.8.6 17.4_Radio_01.01_U11440601_76.03.50611G_F_release_ 439079_signed_2.exe
screenshot




*If not, keep in mind that the RUU will wipe your apps and user data, so you
may still want to wait for the OTA. Remember that after Android 5.0, any
modifications to the software at all will cause an OTA update to fail, so this
RUU is the quickest way back to the stock, fully-updated branch.

Source: HTC Support


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