This (carbon block filter) is Tested And Certified by NSF International against NSF/ANSI Standard 42 for material and Structural integgrity requirements.

Premium Granular Activated Carbon Filter Cartridge is made of a highly porous adsorbent material, produced by heating organic matter, such as coal, wood and coconut shell, in the absence of air, which is then crushed into granules. Activated carbon is positively charged and therefore able to remove negative ions from the water such as ozone, chlorine, fluorides and dissolved organic solutes by absorption onto activated carbon. Universal Industry Standard size of 20” by 2.5” and is compatible with most industry standard Big Blue Filter units.

• [ADSORPTION PROCESS] Granules of activated carbon in appearance may resemble black grains of sand however, you can hardly imagine its power to attract impurities. Every single bit has nooks and crannies that attest to a huge inner surface with Aquaboon GAC replacement cartridge ability to adhere such negative ions like ozone, chlorine, fluorides and dissolved organic solutes and thus making water remain clean.
• [INTENDED USE] No harmful impurities will seep into your blood through the skin while you are taking a bath or just washing your hands. As the 20 x 2.5 inch premium quality GAC coconut shell carbon filter is used where water comes into the house for it to be supplied to every tap. You can also install the one for under sink filtration and in particular combine with RO systems. The product has been proven and recognized by NSF to be safe in food industry.
• [RINSING] When you initially turn on a tap after installing a new cartridge you can notice black or gray suspended particles, carbon fines. While they are totally safe it can be unpleasant for you to have them in your water. Another reason to flush a GAC whole house water filter is turbidity that is just an air carbon tends to release when contacting with water for the first time. To get rid from both issues just pass several gallons of water before putting a new cartridge into service.
• [COMPATIBLE CARTRIDGES] iSpring FG25X4, Premier Water Systems 4pcsGAc, Premier 15pcswf, Hydronix UDF-20, Geekpure GAC-20, Crystal Quest CQERC04024
• [COMPATIBLE SYSTEMS] Geekpure 122-20, Pentek 150560, 3G-STANDARD-34-PR20, 150166, 153013, 158129, 158204, 150009, 150564, Hydronix HX-HF5-20BLBK34PR, HX-HF5-20BLBK34

Here are some of its advantages: 

• Minimal pressure drop. Bing less compact it lets water flow without restrictions. That makes the one be the best choice for your shower. 
• Cheapness. Granular carbon water filters are easier and faster to be made and so they are more cost-effective for you. 

From another side, loose granules of carbon the product has lead to less contact time between water and cartridge for impurities to be absorbed. So, water filter GAC has its place if water quality doesn't come first for you. That is why, it is mainly used for multi-stages purification systems, for example, Reverse Osmosis pre-filtration. 

Made with Premium Quality Coconut Shell Granular Activated Carbon	4 - 6 months filter life	Removes large and fine particles
Activated carbon is positively charged and therefore able to remove negative ions from the water such as ozone, chlorine, fluorides and dissolved organic solutes by absorption onto activated carbon.	Remastered to deliver up to a quarter gallon of water per second with one of the most advanced and high-efficiency filtration systems yet. Enjoy a long-lasting filter that can deliver large quantities of water fast.	Designed with a universal Whole House housings size of 20”. The cartridge can be used in Under Sink Filtration & Reverse Osmosis Applications but not for whole house applications.

Aquaboon 20 x 2.5 Inch. Granular Activated Carbon Replacement Filter Cartridge Reduces: