I missed the original post, but I have a few words if I might be
permitted. Just Liners dot com has several types of liners listed on
their site. I would suggest reading the different types of materials
these liners are made of and their characteristics. Notice UV
resistance on PVC. I would also like to point out the weight of the
different material types has a bearing on shipping cost and handling
after it is delivered to you and when you are placing it in the hole.
You might notice Permalon is the one that gives the weight in the
technical specifications. I also believe what they don't say, they
left off for a reason. Shipping is expensive.

http://www.justliners.com/Permalon.htm

I didn't buy liners from them, but I have an EPDM and a Permalon liner
pond and if I build another pond it will be a Permalon liner.

Regards,

Hal