Hayward SP10841 Auto-Skim In-Ground Pool Skimmer, Square Cover collar allowing 1 1/2-inch vertical adjustment Snap-in weir that adjusts automatically to 4 1/2-inch variation in water level Optional float/by-pass valve Stackable notched extension collar allows infinite vertical adjustment All SP1080 Series Skimmers are available with float valve and equalizer kit to meet specific NSF commercial requirements.