Are not essential polyunsaturated fatty acids that have in common a final carbon–carbon double bond in the n − 9 position. Some n − 9s are common components of animal fat and vegetable oil. Two n − 9 fatty acids important in industry are: oleic acid (18:1, n − 9), which is a main component of olive oil and erucic acid (22:1, n − 9), which is found in rapeseed, wallflower seed, and mustard seed.