The 397 is a replacement for the 661 (full projection) and is basicallty an improved version the new Comfort Plus system. (See below) It comes in left and right styles.

Comfort + is a new pearlescent temperature equalising material integrated into the breast form. Essentially it reduces the body's temperature behind the breast form and so any perspiration is minimised. In practice it provides a comfortable constant temperature for the wearer. (Replaces #661)