Dumbbell Wrist Curls

Sit on the end of a flat bench with your feet about shoulder width apart.
 
With your palms facing the ceiling, grip one dumbbell in each hand. Run your forearms along your thighs, positioned so your wrists, hands, and each dumbbell hang off the end of each respective knee.
 
Let the dumbbells hang down as far as possible to fully stretch the forearm muscles. 
 
Curl your wrist up in a semicircular arc as high as possible. 

Return the dumbbells to the starting position.