Class a surfaces: customers often see the surface, such as a Panel, on the surface, the front of the chassis.
B-class: not moving cases, customers occasionally seen, such as the back of the chassis, side, etc.
C-class: the product when you move or open face, such as the underside of the chassis, such as internal parts of the surface
Important limitations and design requirements deviate from affecting the overall structure or to the customer in the course of using hidden insecurity.
Minor defects: meet the design requirements, without affecting the customer used and during use without compromising security, but the customer is not amused.