"This product saved our beach vacation. My 10 year old daughter broke her arm and had a full arm cast almost to her shoulder. I ordered another name brand from another fast delivery site according to her measurements and it was too big and didn't create a good suction even though it had a pump . Just for the heck of it and to have a backup my mother decided to order this one. My daughter is 51". Her broken arm circumference was 9". She's relatively thin. My mom bought the half arm large cover. IT WORKED WONDERFUL!!! I cut a think stocking and covered the cast first to avoid any sharp edges tearing the cover (although the cover is really durable and thick) and then we put the cover on. We didn't stick it on water to burp it, we just squeezed out the air and it worked perfectly. She swam, jumped waves, used it in the shower. It was truly a vacation/summer/bathtime saver!! THANK YOU!!"