small
Yes, some are.
big
5 to 10 feet
there arms are longer
5 feet .
Gorillas aren't the tallest apes, humans are.
It helps them move quicker
According to livescience.com, male gorillas commonly stand over 6 feet (1.83 meters), and weigh over 400 pounds (181.5 kg). Female gorillas are somewhat shorter, and weigh about half as much. There also exist claims of gorillas approaching 7 feet (2.13 meters) and 600 pounds (272 kg), though these are unverified.
29 inches
Orangatan
probably not, due to the fact it is found where gorillas are not found usually, plus its feet are supposedly bigger than a gorillas.