This is a replacement shower filter cartridge. This cartridge uses 100% KDF-55 filtration media. KDF is more effective on hot water than carbon media, carbon can let contaminants through at high temperatures.
KDF media has been in use for decades and it's an NSF certified material. This media is the most effective media for use in a replacement shower head water filter.
This cartridge should be changed ever 6-9 months, depending on the amount it's being used and your water quality. If more people use it, over a long time, and take longer showers, this filter cartridge will need to be replaced more often.