I like to use the band off the top of an ice cream container for the rim in these bags sew it in then construct the rest of the bag leaving an opening on the side or bottom to turn it through. It is sturdie washable and free. keeps its shape too. Also many sizes just look in your dairey freezer at the market. It also works for those baggs for over your arm chair and you can line it with a paper lunch bag which is eco friendly. Good luck to all