A nice 4 x 4 Matrix Array Keypad, self sticking, with a size of 77 (H) x 69 (W) mm.
The lifespan of the tactile switches is more than 1 million actions. The max. operation voltage is 35VDC. The contact resistance is less than 500 Ohm, and a current of 100mA per switch element should not be exceeded.
A debouncing of >5ms is recommended. Libraries, supporting this keypad, are available for example within the Arduino IDE.