No one...(and I mean no one) not even the manufacturers know what the white translucent material is which serves as the diffusing front panel on a softbox. Oh, don't get me wrong there are many good guesses. But I have spent the last one and a half hours doing deep advanced searches on the net. This is indeed the biggest mystery in photography. I don't think the softbox manufacturers manufacture their own material. My guess is that they buy it from a fabric manufacturer. Let the guessing begin!