I made 5 using wool yarn then wrapped them with strips cut from wool scraps. I stitched them closed but then I got to wondering if I had used 100% wool fabric or was it a blend? At that point, I couldn’t tell since it was scrap. I dropped each in an old knee high nylon and tied it shut. Eventually the nylon will wear out and I wonder if they’ll come apart ? They are supposed to go into the washer with the laundry then follow into the dryer but I can’t remember to add them to the wash very often. I do think they are good in the dryer, however. It’s the washing that felts them so it’s important to do.