My son fell at school and when I went to the orthopedist and saw those dirty casts I was horrified lol so I said to my son I dont want you to have a dirty cast so I made him this. I am not sure what to call it but my friend Jet calls it cozy so COZY it is lol. Just take an old sweater and cut the sleeves off and sew both ends leaving a space to put a shoelace or cord through and thats it pretty simple but it works to help the cast keep clean. Oh I forgot you have to make a hole where the tumb goes so your tumb can get out lol When you put it on tie the cords at both ends to adjust to your arm not to tight.