Mobile phones come in all shapes and sizes but few are as tiny as the Siemens SL55. You can place the SL55 on top of a credit card and see the card's edges all around it. The trick to keeping the size so small is the slide-down keypad, which, when visible, makes the phone a more conventional size.

The good news is that you don't need to extend the keypad to use the SL55, as the buttons beneath the screen can initiate calls. However, all of the keys are very small and quite fiddly.

There's the usual range of features that you'd expect to find on a modern mobile phone. It has tri-band, for using the phone all over the world, and supports MMS, although to get the most out of this you'll have to buy the camera, which clips onto the bottom.

If your mobile phone contract supports it, you can use the phone's GPRS ability to download emails, polyphonic ringtones, logos and screensavers.

You can also get a wide range of games and Siemens bundles the phone with two free samples.

The colour screen is pretty good and works at a resolution of 100 x 80 pixels. It worked well for playing games and can easily display any pictures that friends may send.

A nice feature is the ability to synchronise contact and diary information with your main PC. Unfortunately, as Siemens doesn't supply the necessary cable and there's no Bluetooth you'll have to fork out £30 for the cable to use this option. If you prefer, though, you can buy a docking station that plugs into your PC and acts as a charger.

You shouldn't need to worry about topping the battery up much, as the SL55 gets 200 hours of standby time and 210 minutes of talk time from a full charge.

The SL55's size makes it desirable, and Siemens has crammed in a lot of functions. It's expensive, though, and you have to buy the add-ons to make the most of its features.

Contact: Siemens 0845 740 0700
www.my-siemens.co.uk