This piece illustrates a cross section of human skull, meninges, and brain in accurate proportion to one another in an ‘average’ section where the cranium is around 5.5 mm thick. The dura and arachnoid are closely adhered to one another with the subdural space being only a potential space. The subarachnoid space, meanwhile, is much larger than is usually shown in diagrams, around twice the thickness (2 mm) of the dura+arachnoid.