Le dizayini ehlanganiswe kabili yenkomishi ka-ayisikhilimu igcina isitsha sephepha singavuzi, kuyilapho ifilimu ye-PE yangaphandle ixosha amanzi namafutha, futhi ifilimu ye-PE yangaphakathi igcina umzimba wenkomishi yephepha ungawohloki, iwenze uqine futhi uqine.