Well,it is mainly the Red and the White Oak, but there'd also be different grades of wood, and trees of different species grown in different places in different ways, and dried and cut in different ways,.. all giving a lot of variation in the final timber.
Some of the doors and kitchens may not be real wood, it could be a melamine plastic coating. Pippy Oak would have small pin sized knots, and more colour and variation than some other Oaks
