How to set "Packing Tag" to Sprites created at runtime?

I use Unity 5 UI to display a lot of static images inside a Scroll Rect.

If I have images inside my Assets folder, I can set "Packing Tag" to the same name and number of Batches and SetPass calls decreases dramatically. But in my case I load those images using WWW class.

 www = new WWW(myUrl[i]);
 yield return www;
 mySprites[i] = Sprite.Create(www.texture, new Rect(0.0f, 0.0f, www.texture.width, www.texture.height), new Vector2(0.0f, 0.0f));

How can I set the same "Packing Tag" to all mySprites?