A teardown of the Sony Xperia Z1 revealed that the back cover of the device is the same as the one found on the Sony Xperia Z; the newer model is slightly better protected from water and dust than the Xperia Z is. The Sony Xperia Z1 is the first of a camera-centric line called "One Sony," and as such it sports a 20.7MP Sony G lens...
Source: http://www.phonearena.com/news/Sony-Xperia-Z1-is-taken-apart-reveals-same-back-cover-design-as-its-predecessor_id47445
Source: http://www.phonearena.com/news/Sony-Xperia-Z1-is-taken-apart-reveals-same-back-cover-design-as-its-predecessor_id47445