Flat Bench Dumbbell Flys
On a flat bench, chose a pair of dumbbells that aren't too heavy. Take the arms out, level with your shoulders, elbows slightly bent. Bring the dumbbells together above your chest. Move only at the shoulder joint, the arms are locked. Keep your chest up, shoulder blades together. Maintain time under tension by moving slowly up, slowly down. Really feel the stretch at the bottom of the movement.