The "flip" or "clamshell" design, where the display and keyboard are separated by a hinge, is a popular one for conventional cell phones, particularly in the U.S. Jim Balsillie, co-chief executive of RIM, said 70 percent of handsets in the country have this shape.
"Bringing this form factor to the smart phone category is, we think, very special," Balsillie said.
"Smart" phones expand the features of a regular phone with applications like Web browsing and e-mail access, which is RIM's forte.
The Flip is the successor to the BlackBerry Pearl, which launched two years ago. It has a standard "candybar" shape. Both models have 20 keys and double up some letters on each key, in contrast to the wider, more professionally oriented BlackBerries that have more keys, and assign only one letter to each key.
RIM has done very well with the Pearl, which was its first entry into the consumer smart phone market. It turned the BlackBerry from an accessory for corporate e-mail slaves into a hot item for consumers who wanted a bit more from their phones.
Figures from research firm IDC showed that RIM nabbed 53.6 percent of the U.S. market for smart phones in the second quarter, though that figure was likely inflated because buyers looking at getting an iPhone from Apple Inc. were holding off in the quarter, waiting for a new model to arrive.
In a research note Monday, analyst Tavis McCourt at Morgan Keegan said it was particularly important for RIM to attract new customers by expanding its range of phone designs, or "form factors" in industry parlance. The company is widely expected to unveil a keypad-less touch-screen phone soon, to compete with the iPhone.
The Flip will complement T-Mobile USA's relatively slow data network with Wi-Fi capability, and will even be able to place calls over Wi-Fi, which can alleviate problems with poor network coverage in homes and offices.
Balsillie said T-Mobile USA will be the exclusive carrier for the phone in the U.S. at least through the end of the year. Usually, BlackBerry's phones start on one carrier and are later picked up by the other national carriers.