Our 27' round pool came with a small cartridge filter that struggled all summer. We shopped around and found the Vevor 22" sand filter for way less than half of what the name brands are going for. We read the reviews and some complained about o ring fitment issues. Sure enough, our o ring was slightly too large to properly seat into its groove. A quick Google search reveals to boil a o ring in water briefly to shrink its size, WELLA...it works and no more leaks @! Couldn't be happier with our purchase and our crystal clear pool!! Yay Vevor!!