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.
There are nylon and plastic end bristles in the middle of the natural boar bristles which defeats the entire point of the product. They have not mentioned this in the product description. Otherwise, its a good brush with nice wood.