Amazon calculates a product's star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers and factors that establish reviewer trustworthiness.
It looked sturdy. Build quality was good. But the pistons are so small. It takes about 20 presses to fill a lady Bird cycle tyre which so annoying. For 300 you can buy an excellent air pump in a local cycle shop.