I haven't sold or bought any totes yet, but when I saw the sizes being offered, I immediately gravitated to the 16". I use cloth totes for grocery shopping, and with 4 in the family I can use a lot of totes at once. All of them travel with me inside a huge bag that I made for the purpose. The 18" might be nice for beach towels, but my experience is that grocery store baggers (the male ones - always) grab the huge bag, dump everything else out, and try to stuff all the groceries into the one bag. Smaller bags will keep them from doing that. Can't wait to get my own work on a bag!