The growth of the arm should grow together with the shoulder, back, chest and abdominal muscles to show the overall beauty. If you practice your arms alone, I suggest you bend 8- 12 dumbbells for biceps brachii, 4-6 sets for triceps brachii, and 8- 12 4-6 sets for biceps brachii, which is twice the size of biceps brachii. It is suggested to focus on stretching biceps brachii, and add protein's supplement to make the arm bigger and more stylish.