cartridge media is the same as the indicator spot. to change, simply un-screw the back of the shower rose, take out the cartridge and replace it with a new one making sure any o’rings stay in place, then screw the back on firmly. then turn on your shower water slowly, check for any leaks and it’s ready for use. to increase the cartridge life and water quality of your shower filter, simply reverse the cartridge every 1-2 months, flush the water through for 1- 2 minutes and then turn the cartridge back to its original place. 