One-Shoulder Strappy-Back Long Formal Dress 26266Simple and sweet, this one shoulder long formal dress is a modern style for the girl with a busy social calendar. Whether you're going to prom, a black tie wedding, or another formal event, this long designer dress by Mac Duggal flatters the figure with an unpretentious design. With a fitted look from the asymmetrical neckline to the hem, this long evening gown has one shoulder strap that attaches to two bands that flow diagonally over the open back,