Here's what Innova has to say about the Tern:    

Like the name, this disc has natural turn. Similar to the Archon, the Tern is a fast slightly understable disc that is designed for long shot shaping throws. In the hands of a powerful player, it just may be one of the farthest flying discs due to the long glide and natural turn. The Champion Tern flight numbers reflect a more stable flight. (12|6|-2|2)

Speed: 12   Glide: 6   Turn: -3   Fade: 2