Ko te waea TW/THW he kaitakawaenga, he kaikawe parahi, he maru ranei, he mea weriweri ki te Polyvinylchloride (PVC).
Ko te waea TW te tikanga mo te waea werawera, wai-atete.
Ko te waea THW he werawera, he waea wai-atete, engari he wera wera, e tohuhia ana e te H i te ingoa.