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.
These bags are a bit weaker than regular plastic bags, but that is the trade of for being biodegradable. Once used to handling them a little more carefully they are fine and I have no desire to go back to plastic. They are a bit smaller than other bags sold as 30l though.