Hayward's Commercial HCF series of filters have been engineered to incorporate many new, innovative, advanced features to fit today's demanding applications. Overhead multi-diffuser (36in models only) distribution is combined with a horizontal lateral grid-array. This system improves water distribution over the filter bed resulting in longer filter cycle time, improved filtration and a more efficient backwash cycle. A rapid open/close lid mechanism with positive O-ring seal simplifies operation and ensures long-term durability and reliability.