Open bags with an anti-reflux valve preventing the urine from flowing back towards the stoma are often preferable. There are 1-piece and 2-piece systems available: <li><strong><a title="One-Piece Ostomy Bags" href="https://www.shopostomysupplies.com/c-one-piece-ostomy-bags.html" target="_blank">1-piece systems</a><br /></strong>In 1-piece systems the adhesive and bag are welded together. The advantage of using a 1-piece appliance is that it is easy to apply and the bag is flexible and soft. </li><li><strong><a title="Two-Piece Ostomy Bags" href="https://www.shopostomysupplies.com/c-two-piece-ostomy-bags.html" target="_blank">2-piece systems</a><br /></strong>In 2-piece systems the bag and adhesive are two separate components. If your skin is sensitive, the 2-piece system might be preferable as you do not need to remove the adhesive frequently. The adhesive can stay on for several days while the bag can be changed as required.</li