*** YOU NEED TO REGISTER ON THE FORUM BEFORE YOU CAN ACCESS THE DOWNLOAD LINK ***
INSTALLATION INSTRUCTIONS
- Open link above and skip to the section entitled “FlashTool steps”.
- As you have already downloaded the FTF firmware file, skip to the section where you need to “Flash device”.
XPERIA FIRMWARE DETAILS
Model: Sony Xperia Z1s (C6916)
Firmware version: 14.4.B.0.56_R14C
Region: US (T-Mobile) [1277-0679]
Android version: 4.4.4

Xperia Z1s_C6916_14.4.B.0.56_US_T-Mobile 4.4.4
Sony Xperia Z1s (C6916) Android 4.4.4 firmware - T-Mobile US