First, I'm not in the US (I assume you are), so things may be different here. Until recently all were manufactured locally but the latest batch comes from China

First, I'm not in the US (I assume you are), so things may be different here. Until recently all were manufactured locally but the latest batch comes from China, All containers are semitransparent polyethylene, I can mostly see the contents when looking from the side. The Chinese ones are slightly more transparent than the local product. They're not old enough to develop the film (6—12 months), so it remains to be seen what happens to them over time. They're definitely not PVC—I've chucked enough of the broken ones on the fire over the years and they don't burn with the acrid fumes of PVC (there's no mistaking the choking smell of burning PVC). Incidentally, on occasions when broken containers have left me short I've repaired them by running a soldering iron along the cracks to melt them together. As with Pb/Sn soldering I'll use a bit of spare material and apply it to the cracks. It melts just like polyethylene. You cannot do that with PVC (at least not practically), by the time it gets hot enough it bubbles and turns black and stinks to high heaven. A final point, PVC is now banned here for household use—has been for several decades because of its choking fumes/toxic byproducts of combustion in house fires. Electrician friends who are old enough to remember the PVC insulation days still whinge at its loss, the new insulation isn't as robust or as flexible (stripping the insulation off wire isn't as easy as it was with PVC).