If this wasn't clear, I meant that some products "diffuse" only in space but not phase (so-called polys, and in fact, they are hemicylinders unless placed in a collection), others have varying performance in space and phase, and virtually all also end up absorbing. RPG has often provided relatively frequency-specific information for scattering, diffusion, and absorption for their products. To make things worse, one's understanding of the performance of a specific device may be limited by the availability of only random incidence performance data, which is not the same as performance from a specific angle, nor its performance in a collection or array (i.e. polys when there are multiples). Even in the case of an absorber, only limited information is available for specific incidents and fabric coverings.