They came in 3 sheath sizes when I had mine although that was a long time ago. At night I think I used a larger night bag held in a bucket and can't recall a problem. What I did find was that the elasticated strap they provided to hold the bag in position on my upper leg allowed the bag to slip down after a time. To counteract this I used the elasticated stocking, (available in different sizes) to hold the tube and bag in place. This did help.