To calculate the overall star rating and percentage breakdown by star, we don’t use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyses reviews to verify trustworthiness.
I use these zippers in purses that I make and they are very sturdy. I dropped off the defective order at a UPS store (I didn't have to package the return) and I had an order arrive without the zipper pulls, the replacement order arrived 3 days latter.