As the name suggests, the size is what sets the phones apart from most other Android-based phones. Both models have a 2.55-inch capacitive touchscreen display with a resolution of 240 x 320 pixels. The pro model adds a backlit QWERTY keyboard that slides out from beneath the display, making it bigger and heavier. It measures 90 x 52 x 17 millimeters and weighs 120 grams, compared to 83 x 50 x 16 millimeters and 88 grams for the the Xperia X10 mini.

Both phones run version 1.6 of Android. Sony Ericsson said it will be possible to upgrade them to newer versions of the software, but did not say when.

Other features include a 5-megapixel camera with an LED flash, a standard 3.5 millimeter stereo headphone jack, A-GPS (Assisted-GPS) and an FM radio. The phones can access the Internet using either HSPA (High-Speed Packet Access) or Wi-Fi.

Sony Ericsson has put just four application buttons on the small screen, one in each corner, to make them as easy to reach as possible.

Just like the Xperia X10, the two new phones also feature support for Timescape, which is Sony Ericsson's application for keeping track of text messages, missed calls, and Facebook and Twitter updates, the company said.