SOYO 40 GB SlimEx Onyx USB 2.0 Slim Hard Drive (FM-SY-SLIM40GB) Dimension is about a size of a business card and weighs about 3.35 ounces makes the drive one of the smallest portable hard drive in the market. With the retractable USB cable, you can take it anywhere you travel Perfect compliment for your mp3 back up, notebook to desktop file transfer, and store your pictures or files while roaming. The unit sports a USB 2.0 interface, which without a doubt offers the best connectivity around today, It is also both PC and Mac compatible. In addition, the drive does not require any power adaptor at all, as simple as plug and store. Magnesium Alloy Casing, Light Weight & Easy to Carry; No External Power Supply or Battery Required Overall Dimension: 3.9" Length by 2.4" Width by 0.4" Height