Hayward C550 Easy-Clear Filter 55-Square-Foot Easy-look lid access design provides simple entry to service the cartridge element ; length 55-square-feetts Built-in check valve prevents accidental loss of pool water when cartridge is being removed for cleaning Unique safety-catch prevents over tightening of the cover and unwanted entry into the filter Cartridge element is uniquely designed of high quality reinforced polyester and a molded center core for easy cleaning, high flows and long life Union connection allows pump or filter to be removed quickly and easily for servicing systems