I got the medium. It's cheap and fits perfectly over carry on suitcase. I wouldn't get this for a carry-on since it's with me in the cabin. However, I decided to check it in for this trip and wanted extra protection since I know how luggages can be tossed around. This cover offers that extra layer and prevents scratches and damages. Easy to use and uses a zipper enclosure. The zipper seems to be very sturdy and not those flimsy ones.