P2 and P4 denote hardness if I know it well, and it can't be determined at first glance. The Ytong A + designation, for example, means energy rating. At first glance, this is not the clearest feature either. I don't think it's very easy to tell which one is which, because with these data, such as A +, there are a lot of Ytong products, as well as P2 and P4.