5 W, but I bought the 9 M because in the store they did not carry the wide widths the 9 M fit great - no issues with width whatsoever; the only problem is that I tightened the straps that go behind the heel and the ends overlap the velcro strip and hang loose. The battery life is the best! I usually wear a medium, but ordered this in large because I like roomy nightclothes. Have had the blue pair the longest. Its no Suunto or Garmin or Casio, but for the price point it meets my needs as a GPS watch. Also, the description does not state this, but it comes with the carbineer shown in the last picture. I did change the silicones to the smallest The sound is just ok on these, No bass at all. The microphone quality to some people when I talk to them is very low or sounds like I am speaking far away from the product. I should have left them home. These are much more comfortable and fit *my feet* perfectly, with the same amount of space between the toes and front of the sandal as their is between the heel and the back.