Sorry, I don't agree with this at all. I bought one from you (Murgen - direct seller) via Amazon. There are no pins on the charging points, so they cannot reach the charging points on the side of the Xperia Z to charge the phone. The unit is therefore useless. To me, this must be evidence of an absence of quality control, or that the pins are so flimsy that they cannot withstand even the first use. I inserted the phone into the case carefully, in accordance with the written instructions. There are different quality devices, and on the basis of my experience Murgen are at the bottom of the heap! Potential buyers beware.
Might be useful for practicing your soldering skills I suppose, to do the job that Murgen don't. Looks like another £40 for an electrically conductive adhesive to DiY! Not amused. I think you're better off with a separate booster charger which uses the micro USB charging point frankly, rather than this gimmick. Apart from the charging pins it's solid plastic I suppose, but the case of mine is quite loosely put together and the battery is loose within the case. You can feel it move.