Are MidWest-Canvas solar covers any good?

I have a chance to buy one a a really good price.

http://www.amazon.com/MidWest-Canvas.../dp/B004VU8J08

thanks

They are not actually canvas. The opaque solar covers work by conduction of heat from the top to the water. Circulation is required to move the warmed water through out the pool. They can work well, though, personally, I think the clear covers work best, directly heating the water and further down. I don't know the brand.