The Sony Xperia T3 was officially announced today as the "the world's slimmest 5.3" phone." Its actually quite hard to challenge that statement, as there aren't many 5.3" handsets around to compare it with.
In any case, the device is extremely thin with measurements of 150.7 x 77 x 7 mm, built around a stainless steel frame, with an aluminum power/lock key on the side. The IPS-LCD Triluminos display has a screen resolution of 720 by 1280 pixels, with a 277 ppi pixel density. The handset is powered by a 1.4 GHz quad-core Qualcomm Snapdragon 400 processor with 1GB of RAM. This may not be the fastest processor in the market, but is still quite capable.
Other specs include 8GB of internal storage which can be expanded through microSD, an 8 MP Exmor RS rear camera capable of 1080p video capture, a 1.1 MP front-facing camera capable of 720p video capture and a 2500mAh battery which Sony promises will last 12 hours and 46 minutes for talk time, and 8 hours and 14 minutes for video playback, which is quite decent.
You get Android 4.4 KitKat out of the box, customized with Sony's Xperia UI and you can pick the device up in three colors - black, white and violet. The handset is expected to be available by the end of July and should be priced as a mid-range device.
source - Sony