The Sony Ericsson Z520i is a mid-range clamshell mobile phone, with interchangeable covers and flashing blue lights to alert you of a call or message. It's marketed as the ultimate customisable phone -- you can change the covers on the outside and tweak a variety of internal features, such as the wallpaper or flashing lights.
We found the Z520i free on a monthly contract for as little as £16 a month in the Carphone Warehouse on O2 and Vodafone. You can also buy it SIM-free for around £130.
The Z520i is a small clamshell phone measuring 46 by 83 by 24mm and weighs 94g. It's a simple looking mid-range phone that feels light and small in the hand.
On the front section of the handset you will find a VGA camera and a 25mm (1-inch) external 4k-colour screen, surrounded by an exchangeable cover. Our white model came with extra fascias in pink, but when we tried to change the front cover, it felt like it was about to break in half. On the back section of the phone is another exchangeable cover that hides the battery underneath. This cover is much easier to remove than the front one and simply slides off. You can buy extra covers in a variety of colours if the ones provided aren't to your liking.
At the top of the back section of the phone, you will see a silver speaker that plays your ring tones and provides the speakerphone function. You will also see the same unmistakable loop aerial as the W550i, which makes holding the phone awkward but hanging it from your neck easy.
On the left and right of the phone there's a strip of silver plastic that runs around the phone and into the loop aerial at the top. On the left of the phone you'll find the shutter and volume buttons in addition to the infrared port. At the bottom is the standard Sony Ericsson charging port. Unfortunately, the shutter button has a life of its own and it will take pictures of the inside of your pocket if mistakenly pressed.
The hinge on the phone feels strong and is unlikely to break if you drop it. Opening the phone is easy to do but does require two hands. Once you have opened the Z520i, you will see the internal screen, which has a resolution of 128x160 pixels and displays 65,536 colours. It's not as bright as the Sony Ericsson K750i's screen, but it is sharp. On top of the screen a small silver grill protects the ear speaker.
The interior of the phone is completely white except for the four-way navigation button, which is silver and round, with an OK button in the middle. This may cause some problems if you wear make up or eat a lot of chocolate, as it might rub off and stain the pristine surface of the keypad.
At the top of the keypad, on either side of the navigation key, there's two soft keys and a return and cancel button underneath those. The number keys are well sized and easy to press and the Web browser and power button are right at the bottom so you won't press them by mistake.