I bought this to store my single down comforter. In the reviews, it said that “this series uses a belt to secure the comforter in place, so it's best to choose one that matches the size of the comforter”, but I wanted to store my other blankets and winter sheets in there as well (lol), so I chose the M size. As a result, it's not like it's useless if the size is different! but I thought it was best to choose the right size. After six months of storage, we recently had our first seasonal change of clothes, and the clothes were stored neatly without getting moldy or being invaded by insects. I think they're okay because they feel quite sturdy when you touch them, but I hope the non-woven fabric doesn't deteriorate and that I can use them for a long time.