Product review (3 stars): Both NSF 42 and NSF 53 certified
Good quality but too expensive to class as good value for money.
Water flow is so-so!  People used to filters only adhering to NSF 42 will be used to higher flow and are likely to complain about the flow through this filter.

Bottom line:
NSF 42 removes chlorine and odors.  NSF 53 removes more harmful chemicals too but has finer/additional filtration that further reduces water flow.
If your primary concern is flavor, get a far cheaper generic filter - most adhere to NSF 42 and will have faster water flow rates.
If your concern is safety and filtering of dangerous chemicals, go for a filer certified to NSF 53 such as this one, but expect slower water flow.