The most significant feature in the K660i is the inclusion of HSDPA high-speed data. This makes web browsing and multimedia downloads much quicker than standard 3G, and it also means that the K660i can be used as a broadband modem for a laptop. The other important feature is an improved web browser, designed to be much more like a PC browser, complete with a pointer and scroll bars, along with a screen that can be used for web browsing in either portrait (tall) or landscape (wide) modes.
These two features aside, the Sony Ericsson K660i is otherwise pretty standard fare. It's a 3G phone with a 2" 240x320 pixel display, 2 megapixel digital camera, video calling, stereo Bluetooth, a multimedia player, FM radio, email client, web browser and R.S.S. feed reader. There's a mapping application too.
The K660i's memory is expandable using Memory Stick Micro (M2) cards with 256Mb included in the box. Underneath is a quad-band GSM 850/900/1800/1900 MHz phone with UMTS 2100 MHz, plus GPRS, EDGE and HSDPA data. The K660i measures 104 x 47 x 14.7 mm and weighs 95 grams, which is pretty light for a 3G phone.