The picture below demonstrates the difference between Traditional Apron Front sinks (bottom picture) and the New Cygnet FSR3321APF-7 Genoa that is made to fit existing cabinets without major carpentry work. The sink also fits new cabinets.
The advantages of the Genoa is it fits in most existing cabinets. The Apron is 6 3/4". You remove the false drawer front and the apron fits over the front.