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.