Types of Adjustable Dumbbells

Triceps
The scle, the triceps, which extends the arm when it contracts.

The tricep kickback is easiest to do with the support of a bench. The tricep overhead extension can be done with one arm, or two. You can of course use more weight if you're using both hands.

You can also work the triceps without dumbbells, with tricep dips. These can be done by supporting your hands on a bench.

Shoulders
The deltoid is the large muscle forming the shoulder cap, and serves to raise the arm from the side; it runs from the shoulder-blade to the middle of the humerus.

The Alternate Front Raise blasts the anterior (front) deltoids. The Dumbbell Lateral Raise targets the medial (side) deltoids. Bent-over Lateral Raises intensely works the posterior (back) deltoids.

Upper Back
The chief muscles engaged in lowering the arm again are the latissimus dorsi (lats), which runs forwards and upwards from the back and side of the chest wall to be attached to the front of the neck of the humerus; the coraco-brachialis, attached to the middle of the front of the humerus; and the pectoralis major, which forms the front fold of the armpit.

The latissimus dorsi is the widest and most powerful muscle of the back. Properly trained its what gives bodybuilders the sought after V taper.

The lats can be worked out with a one arm dumbell row and also a bent over row.