This is the first year I'm going to try using pool pillows when I winterize my in-ground pool to help the cover stay mounded up in the center. It drives me crazy when leaves and debris blow onto the cover and accumulate in the center where the cover is touching the water, decomposing and filling my pool with phosphates. Then I have to hurry up and pull the cover off in the spring before the algae goes nuts. I'm hoping this gives me a little more breathing room in the spring to open the pool when I see fit, not right after the first hottest day when the algae starts blooming. I have a large pool with a big shelf, so this little pillow is for the shelf area, and I have 2 4x15's for the main pool. Since it's not time to close the pool yet, I obviously can't comment on how this held up over the winter, but I did fully inflate it and let it sit for 24 hours. In that time, no air was lost, so I am confident that it will hold air at least. I appreciate that it came with grommets in all 4 corners, some rope, and a couple of patches.