This keypad has 12 buttons, arranged in a telephone-line 3x4 grid. It's made of plastic with sturdy plastic buttons. The keys are connected to a matrix so you only need 7 microcontroller pins (3-columns and 4-rows) to scan through the pad.
There's a great Matrix Keypad Arduino library that will work great with this item with minor adjustments. It comes with 7 header pins pre-soldered on for easy plugging. Starting from the left there are three column pins, and then to the right are the four row pins.