The attached part is representative of the blood volume within major vessels in the body. I am attempting to offset each of these surfaces by 1 mm, and then delete the blood volume, to re-create the actual vessel. I started with an imported .stl and used ScanTo3D to create the surfaces. I then filled the ends of the surface to create the current solid body. I hoped to shell outward, but it throws an error and highlights the faces unable to shell. So, I took the remaining faces and tried to offset the surfaces. I hoped I could offset most of the outer surface and then simply fill in the holes. However, that didn't work. I can offset some of the faces by selecting them one-by-one, but this is a VERY tedious process. Anyone have any suggestions?