There are three main standards for wood furniture that are produced in Indonesia  Class A, B, and C.
Class A is the best it is characterized by a straight and consistent colored wood grain with no knot marks.
Class B may have wood grain that is not straight, the color of the wood may be inconsistent, and it may have a certain amount of knot marks.
Class C is the bottom class that is characterized by having varying grain quality and color, frequent knot marks and other blemishes.