This is one of the most popular and in many ways controversial masks on Amazon. WWDOLL is one of the many KN95 style masks manufactured by Chengde Technology co, which the CDC has called out multiple times for producing counterfiet and subpar products.
Why did this mask fail?
This particular mask did pass both filtration and breathability tests, but one of the basic parts of the KN95 standard requires putting the words GB-2626-2019 on the front of the mask, which this mask obviously doesn't have.
There are many other tests a mask must pass beyond filtration and breathability according to the full KN95 standard, so if they didn't abide by this simple one...what else didn't they do?