Like the tiny 1GB NWE107, the 512MB NWE405 continues the Sony tradition of delivering very compact, flash-based music players with excellent battery life.

Sony claims that a mere 3 minute charge of the NWE405's rechargeable lithium ion battery will provide the NWE405 with 3 hours of battery life. We tested this and found a 3 minute charge actually gave us almost 4.5 hours of continuous playing time. The NWE405 has a maximum of 50 hours of battery life, leaving the 12 hour life of the 512MB Apple iPod Shuffle far behind. Fully charging the unit takes about 2 hours, and involves connecting the NWE405 to a PC with a USB cable.

Measuring 85 x 29 x 14mm, the NWE405 is slightly larger than a cigarette lighter and can fit comfortably in a pocket or can be hung around the neck. While it weighs only 47g, the player has a sturdy feel to it and is encased in a striking transparent plastic casing with a solid plastic backing. The plastic casing contrasts well with the three-line blue OLED display, which is suitable for both strong and low light conditions. The display on the NWE405 can be toggled to show a clock, a "Bubbles" screensaver or track information and can be configured to turn off after 15 seconds to save power.

The controls on the NWE405 are somewhat unusual. There is the standard play/pause button and buttons for accessing the display and searching options on the front of the unit. However, Sony has also included what it calls a 'Shuttle' button, which can be pulled out and rotated to fast-forward and rewind songs or albums. This control took a little getting used to, and users will have to read the manual as using it isn't intuitive.

The NWE405 had excellent sound quality and the supplied headphones were exceptional. The player supports the usual repeat, shuffle and basic equalisation features. It plays music files in MP3 format, as well as WMA and the Sony-proprietary ATRAC3 and ATRAC3plus formats. Unfortunately for users of Napster, the NWE405 doesn't support protected WMA files.

Potential buyers should be aware that the advertised 50 hours battery life applies to playing back files in the proprietary ATRAC3 format, which are encoded at a lower quality (66Kbps). When playing back MP3 files at the standard encoding of 128Kpbs, the unit provides a solid, but reduced, 40 hours of battery life.

For all its qualities, the unit is not very convenient. Firstly, a USB cable is needed to connect the NWE405 to a computer, so you would have to carry this cable around for whenever you wanted to transfer music or charge the player. Secondly, music files cannot be 'dragged and dropped' directly onto the player in Windows Explorer, as is the case with many other MP3 players. Instead, users have to install Sony's SonicStage software, which imports all music files from your computer (or a CD) into its library and can then transfer them to the player.

Sony also encourages users to convert MP3 files into its proprietary ATRAC3 formats, which is both annoying and time consuming. CDs for example, can only be imported into the ATRAC format. It took us about 30 seconds to convert a 5.2MB, 192Kbps MP3 song into 132Kbps ATRAC3, with a resulting file size of 3.6MB.

The NWE405 can be used as a USB storage device and files can be dragged and dropped onto the device using Windows Explorer. This includes music files, but they just won't be recognised on the player as music files until imported by SonicStage. Additionally, some MP3 players, like the Samsung YP-T8Z allow you to hook up two MP3 players to transfer songs directly from one player to another. But when plugged into the Sony, the Samsung could neither recognise nor transfer any songs.

The NWE405 is not exactly brimming with features. It would benefit from voice recording, an FM tuner or PIM capabilities, which can be found on other players for a similar price.