There are three different types of acyl-CoA synthases[2] which can help make 3 different lengths of acyl-CoA. For example, medium chain acyl-CoA synthase is made to work upon 4-11 carbon fatty acids to make 4-11 carbon acyl-CoA. A different type of Acyl-CoA synthase is used for a 11-20 carbon fatty acid to make it into a 11-20 Acyl-CoA.