Have to turn up my new one louder now. I check and there it is, mismatched key and lock cores! The one that i received unfortunately had a very strong of chemical odor to it, so i had to return it. 5 and 9) and often order the larger size when shopping online. 5 the better they feel. They are easily the most comfortable closed back headphones I own. I probably could have purchased a size down. These are high quality, comfortable wireless earbuds. One shoe chart on internet says 9. Yes, I have to put it together, but the instructions are better and the overall quality of components is higher.