Stretchy straps ensure a good fit. These should give me a bit more to go on, as I am still new to this. Ive owned the Sony MDR-EX15 for 5 years and they were great, unfortunately I ran mine through the washer/dryer and, although very clean, they were fried. I wear a wide size but this is just a little too wide so slips on my heal. I gave them the headphones, and played them the two clips that I thought sounded different. These fit, but feel just a smidge small. But you cant use it on the nice quality thick wired headsets like plantronics. A disaster, so sadly I have returned it. I’m going to hang on to this product anyways. As another reviewer pointed out, the cross bars pieces can only be inserted into the groove from the rear of the vehicle.