But I?m too lazy to return. Have to flip the device on its head while charging. I gave it 1 start for warmth as that question doesn?t make any sense to me. I usually wear between and 7. I was skeptical at first, as I have purchased other chargers similar to this, only to have them fail. So sonically they are a 5, isolation wise they are a 3. I am not getting paid for this review nor did I receive this product for free so that I will give a good review. I didnt want a full size laptop. Because they are so flimsy, I never take mine out of the house. These are extremely comfortable sandals to wear.