Erm carbon removes chemical impurities out of the water, water polishing is the term used to finely filter the water
'Polishing pads' commercially available for some filters are a really dense high PPM grade kinda wool, they do a better job at filtering, but hence clog quicker.
The quick filter attachement is good as it takes 5 mins to remove, clean, and put back in, whearas changing a fine filter pad in a canister can take a fair bit longer sometimes.
Very very effective. increases maintenance intervals of my fx5