Collagen Casings take the place of using natural hog or sheep casings. They can be usd for fresh or smoked sausages. They are made from beef protein. There is no preperation necessary. Just put them on your stuffing tube and before you know it you will have uniformly sized sausages! Use the 32mm size for Bratts or Italian links. The 21mm size are great for breakfast sausage. 19mm and 17mm are snack stick size.