Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
I took a punt on buying this filter as I wasn't sure if it would fit my coffee machine but it was exactly like the one I got with the machine when I bought it! The price of the filter was a bonus too as it was a lot cheaper than other sites I looked on! Very happy.