Pre-cut wafers have an existing hole already cut out of them, preventing you from having to cut the opening yourself. This type of wafer is best suited for people whose stoma is round and completely healed. Pre-cut wafers are not ideal to use right after ostomy surgery, as your stoma shape and size can change. Pre-cut flanges can save you time, since you do not have to cut and fit the wafer to your body. You will need to measure the size of your stoma and choose the wafer size that will fit best. If the wafer size is too small, it can irritate your stoma. If you choose a wafer size that is too big, it can alter the fit and cause leaks.