*** YOU NEED TO REGISTER ON THE FORUM BEFORE YOU CAN ACCESS THE DOWNLOAD LINK ***
INSTALLATION INSTRUCTIONS
http://www.xperiablog.net/2015/03/17/guide-to-installing-xperia-lollipop-using-xperifirm-and-flashtool/
- 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
This is official stock Sony Xperia firmware.
Model: Sony Xperia C4 (E5306)
Firmware version: 27.1.A.1.106_R3A
Region: US (Generic) [1295-8051]
Android version: 5.0

Xperia C4_E5306_27.1.A.1.106_US_Generic 5.0
Sony Xperia C4 (E5306) Android 5.0 firmware - Generic US