Beware not all 12 mil covers are the same thickness or quality!!
I recently purchased my third 12 mil solar cover. The previous two both lasted 5-6 years. Both my previous covers and the new one had 7 year warranties. But I ordered this new blanket from a different supper because it was a little cheaper.
When the new one arrived I knew immediately something was wrong as I could lift it very easy, where as with my last two I could not handle it as easily, so I suspected the new one weighed less. Then, when rolling out the new cover it was undoubtedly thinner and more flimsy than my past two covers.
I called the supplier and they assured me I received a 12 mil cover.
So I borrowed a digital micrometer (accurate to 0.1mm) from an engineer friend. I measure my old 12 mil cover and to my surprise it was 24 mil, but if I measured the thickness of the top layer and bottom layer where a bubble has been cut in half, then each layer was 12 mil. On my new cover, the total thickness was only 12 mil and each layer was only 6 mil. So my suspicion was confirmed, this new 12 mil blanket was half the thickness of my previous two!
There were many weeks of discussions with supplier, they told me things like:
“12 mil doesn’t really mean 12 mil” and
“You can only measure the thickness with a laser micrometer” and
“we weighed the blanket before we shipped it and it is the correct weight”
Finally I told them: “order a 12 mil sample from my previous supplier and compare it to your 12 mil cover, the difference in quality and thickness will be undeniably noticeable”. A few days after they received the sample they agreed to refund my money in full. I am not sure if they are pulling that blanket from their inventory, or if they just want me to go away.
Bottom line: Always request a sample before you buy a solar cover.