One of the local pool stores sells them for $29 each, and the gave me a good discount off of that price when I bought 9 of them. it would take 12-13 to cover my pool fairly completely. I used 7 of the 9 rings I bought this spring covering about 50-60% of the surface area. I put them away a few weeks ago because the water was getting too warm (it was up to about 95.)

I've had a bubble style cover before, and I'd rate the rings at 60% coverage to be about as effective as the bubble cover was at 95% coverage. In AZ, a normal solar cover is good for 1 season before it starts to fall apart unless you take measures to protect it from the sunlight and heat.

When new, the rings are a bit of a pain to get to flatten out. The instructions on their web-site are better than the ones that came in the package.

Storing them is a bit of a challenge. You can't stack them in the sun or the ones in the middle will melt from the heat gain.

Since I stopped using them on my pool, I slid them under my bed