This Pac is designed for use with the POOL FROG XL PRO Sanitizing System. It contains 4.6 pounds of Trichlor (chlorine) providing hassle-free water care for in-ground pools up to 40,000 gallons. The pre-filled Pac offers no mess, no guess, and no stress handling of chlorine. Plus the unique erosion design and ten setting control dial allows the chlorine to last longer. When used with the FROG Mineral Reservoir, you can lower your chlorine use up to 50%.* *Compared to the miniumum EPA recommended chlorine level of 1.0 for a stabilized swimming pool.