Combine arugula, balsamic vinegar, grapefruit, parmesan shavings and pepper in a bowl. Set aside.
Cut the flatbread into 16 equal crosswise slices.
Combine grated parmesan and oil and brush over one side of bread strips.
Broil for 35-45 seconds or until golden.
Turn bread and brush with parmesan mixture and broil one more minute.
Cross 4 bread strips on each serving plate. Top with arugula mixture and serve.