As I could not find these shoes anywhere locally, I had to use trial and error to get to the right size. I returned them for a refund primarily for this reason but I wasnt happy with the quality of the item as mentioned above. Insert the bars, with brackets attached, into the slot on the ?roof? of the car. Based on the reviews about how the slippers are too big I ended up getting the large but they were HUGE! It has a built in microphone as well, so dont bother buying a seperate mic. And whereas other stainless steel had irritated my third hole, these do not. É muito confortável e super leve. I am replacing it with a Panasonic UB820. Unfortunately it wasnt meant to be. Also it is adorable so made my ?bump? pics I took really pretty as well.