Wide arc creates maximum horizontal adduction moment at the bottom, stretching the pec fibers under load. The flat bench position provides a different angle than the low pulley fly.
Maximum stretch at the bottom — the wide dumbbell arc creates the longest pec fiber length under load.
Horizontal adduction emphasis — the fly pattern isolates the pec's primary function (horizontal adduction) without triceps involvement.
Complementary to cable — dumbbells provide peak tension at stretch (bottom) while cables provide constant tension throughout.
Placed fifth to complement the cable fly with stretch-position emphasis.