The Bella is an ornamental (embroidered and sequined) version of the Giesswein Veitsch, and was intended to fit the same. For my wife, a 7.5 to 8 US foot fits a 38 length in this shoe; we verified it at a local shop in the Veitsch, which is the same shoe, just a bit plainer looking. These look like something you'd buy in Hollywood or Aspen.
BUT: a call to Geisswein before placing this order verified that they recalled the Bella because this entire batch was manufatured a bit too low cut and narrow, compared to the Veitsch. Shoes.com decided to close them out at a large discount rather than send them back; business is business, and their return policy guaranteed our satisfaction. So we ordered them expecting them to fit tight and need some break-in, as she has a medium width foot.
So they did indeed fit tight, but patient break-in, with wetting the wool over the instep and wearing them a couple of hours at a time, made for a perfect fit. If your feet are not too wide, and you want a distinctively classy looking slipper with the great Birkenstock-like footbed, get the right length in these and be patient during break-in.
Also note that compared to Haflinger, these have a mid-layer between the wool layers at the toe to prevent toes from tearing through the wool. My wife had previously torn through her Haflinger version of this 'boiled-wool' slipper. You won't feel that protective layer, but it makes these slippers very durable. Overall, a fantastic quality slipper with great arch support and distinctive styling, for the right foot.