Opening width: 40cm (ignoring the parts that stick out). Flat to the wall: Yes, but a mantle/beam is needed. This fireplace is for decorative purposes only. As you would expect, fireplaces of this age can often come with some small, natural imperfections in the metal. The nature of cast iron can mean that sometimes there are some small irregularities in the patina.I believe that this adds to the character of our fireplaces. If you have any questions, please feel free to reach out!