This is a Magnetic Charging Dock for Sony Xperia Phones.
The Dock consists of two pices.
1. The Main Body
2. The Slider
You will have to buy the usb to magnetic charging cable if you want to charge your phone through this dock.
You will need both these pieces. After inserting the Magnetic Charger in the Slider, slide it in to the main body. the rails in the slider should guide itself for perfect fit.
NOTE: This is just one part of the Sony Xperia Magnetic Charging Dock. This is the Body. You will also need to second part (Slider), to be able to charge your xperia device with a USB cable.