How can i resize through script the size of box collider

I'm adding prefabs from the resource folder and i check if the mesh contains childen and give every child a box collider. The problem is that all the box collider are of scale 1 1 1 that means if i have a skeleton body it causes a lot of problems . This is how i assign the box colliders :

            foreach (Transform g in obj.GetComponentsInChildren<Transform>())
          {
             BoxCollider MeshCol = g.gameObject.AddComponent<BoxCollider>();
          }

how can i adjust each box inside to match the dimension of the children of the meshes.?

I have tried using mesh collider and skinnedmeshcollider instead but even after turning convex on it didn't work .