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 found the 6.5cm blades disappointing - too short for my daughter's hair. I must point out the product was advertised as 6.5cm so it's my fault I never realised I needed longer blades. Apart from this the quality is fabulous.