Hayward C1200 SwimClear Plus Cartridge Pool Filter, 120 Square Foot Single piece injection-molded base and body provides added strength for reliable, corrosion-free performance Single locking knob securely fastens head to filter tank, eliminating bolts or clamps Attractive, durable filter head may be rotated to conveniently position pressure gauge and manual air relief Extra-large cartridge element with New precision engineered extruded core provides extra strength and maximum flow