GAC Granular Activated Carbon 2.5"x10" for Water Filter RO,Aquarium,DI and other Standard Water Purifier Systems 2 PACK|cartridge pen|filter clothcartridge box - AliExpress
AquaFlo 2.5"x 10" Granular Activated Carbon Filter / Part# 26277 - the water guys
KDF/GAC Replacement Water Filter Cartridge | Best Filters