Rio today introduced the Rio Nitrus 4GB MP3 player, a new player which is built on the Rio Nitrus 1.5GB MP3 player platform, keeping the pocket-sized design along with more than double the memory and weighing less than two ounces. The new player supports USB 2.0, can playback over 2000 WMA songs (132 hours of music) on a built-in 16-hour LiON rechargeable battery, and includes a five-band parametric equalizer. The Rio Nitrus 4GB will begin shipping this month for an estimated street price of US$249.