The RAZR has proven very profitable for Motorola. Over 50 million RAZRs shipped since its release in 2004. Now the manufacturer hopes to build on that success, through the model's four descendants.

To summarize Motorola's and CNET's information:

• The new RAZR V3xx and Maxx maintain their predecessor's famously thin clamshell profile, and boast HSDPA capabilities. The MAXX is the higher-end variant, featuring music playback controls below its external screen and a 2.0 megapixel camera.
• Narrower but thicker than the RAZR, the clamshell KRZR comes in two variants, also featured in Flash. The K1 works on GSM networks and has better multimedia functions. CDMA users will have to do with the K1m. Both feature reflective finishes, so you can blind people or signal a rescue plane under bright sunlight.
• The sliding RIZR is music-oriented. Supported formats include "MP3, AAC, AAC+, and AAC+ Enhanced."

All four phones come with a microSD slot, capable of accepting 1GB memory cards. The KRZR and RIZR are now available, with the other two promised by the end of the year.