I bought this pillow to help raise my pool cover to keep it drained. I should have bought two, one for each end and side of my oval pool as trying to center this animal up under the cover proved to be very difficult by ones self. Needed the help of two big teenage football player sized young men. Slipping it under a heavy wet cover is a bit difficult. Filled this up using my shop vac by placing the hose on exhaust port. Closing the fill port cap was slightly difficult as it is a large diameter snap in type cap. Lost some air dealing with it but not enough to matter. It's a good product and I will be buying another one as it is easier to install from the corner than trying to install the one to the center.