Bounding box details... what's the size?
What determines the bounding box size of a mesh?
While sculpts ultimately have their bounding boxes that can be adjusted using a graphics program, or even altering the sculpt itself in a 3D program, you are unable to modify the bounding box of a mesh. This is determined when the mesh is uploaded, and most creators of mesh will do their best to keep the bounding box sized correctly for the mesh to help reduce the prim counts for the mesh. Because each mesh is different, the bounding box for each mesh will be different as well. Just as you can see the bounding box for a sculpt by hitting the stretch tabs in the edit window, you can do the same for a mesh to get an idea.