Film was delivered quickly! Basically it is a "bubble wrap" as they are known as packaging. Above blue, black bottom. Reared it warms the surface water (ca 5-8cm) in sunshine tidy. For uniform heating, it makes sense from the filter and allow to run. What is not so nice, the film is right on the water. Everything accumulates on the film ends up eventually in the water when they are pulled down. Best to make 2nd. But otherwise effective, affordable pool heating. Now have up to 28 ° C water temperature (12000L)