Is this a good power adapter?

Using Arduino IDE 1.x
1

I have this Univeral Power adapter at home, was wondering if this would be okay to use with the Arduino Uno. And what would be the recommended voltage to use. It also has a polarity switch, which is the proper setting. Wanted to ask before I risked frying my board.

thanks

2

7.5 or 9 V should be o'k. Internal pin - positive, but don't worry much, there is a protection for reverse polarity on pwr-in connector