I don't know how you'd go about finding the answer to that. One problem is that there is not any test we've been able to discover that distinguishes good liners from bad ones, except for the "test of time"!

I've even talked to one of the engineers at a vinyl sheet material manufacture -- they make, on request, both high and low grade materials, and he couldn't offer any suggestions. Obviously, he couldn't tell me that, yeah, we sell the junk material to these three companies. He did tell me that a number of companies buy both high AND low grade material. A few companies -- I think, but am not sure, that Plastimayd is one -- are known for better grade liner material.