4.5" diameter UDF GAC granular activated carbon filter cartridges are also known as large diameter and big blue filter cartridges, this type is refillable with standard size of 4.5"x10" and 4.5"x20", compatible with most standard big blue filter housings, the carbon is NSF certified coconut shell carbon. Specification 4.5" diameter UDF GAC granular activated carbon filter cartridges are also known as large diameter and big blue filter cartridges, this type is refillable with standard size of 4.5"x10" and 4.5"x20", compatible with most standard big blue filter housings, the carbon is NSF certified coconut shell carbon. Good at removal of disinfection by-product like chloroform and THMs. Suitable for areas using surface water as source water and chloramine as disinfectant. Features NSF Certified coconut shell activated carbon High effect on chlorine and organic pollutants Low turbidity from carbon dust Refillable design Technical data Maximum temperature: 140F (60C) Maximum flow rate per 10: 4gpm (15.14L/min) Capacity: 25,000 gallons - 6 months Caution: Flush for 30 seconds before use. Do not exceed the maximum flow rate to maintain sufficient contact time.