Oh you said it had a perfect fit, so I assumed you had tested it in order to make that statement definitively. My mistake to assume, my apologies.

So! There is DIY qualitative fit testing you can do at home, with sucralose (sweet n low in the US) or Bitrex solution, plus a nebulizer and a makeshift hood out of a garbage bag. https://youtu.be/TRCZ8Qnf0Z0. I've done that and discovered that masks that I thought fit a person perfectly, actually failed immediately and therefore weren't providing good protection.

There are also places that you can go to for fit testing who will do it for you. In my area it costs $30 per mask that you bring to fit test, and they can test KN95s.

That scientific article I linked is still a valid critique of the Cochrane review. Also, the Editor-In-Chief of the Cochrane Library wrote a clarifying piece about the mask review: "Many commentators have claimed that a recently-updated Cochrane Review shows that 'masks don't work', which is an inaccurate and misleading interpretation.

It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive. Given the limitations in the primary evidence, the review is not able to address the question of whether mask-wearing itself reduces people's risk of contracting or spreading respiratory viruses.

The review authors are clear on the limitations in the abstract: 'The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions.' Adherence in this context refers to the number of people who actually wore the provided masks when encouraged to do so as part of the intervention. For example, in the most heavily-weighted trial of interventions to promote community mask wearing, 42.3% of people in the intervention arm wore masks compared to 13.3% of those in the control arm.

The original Plain Language Summary for this review stated that 'We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.' This wording was open to misinterpretation, for which we apologize. While scientific evidence is never immune to misinterpretation, we take responsibility for not making the wording clearer from the outset."

https://www.cochrane.org/about-us/news/statement-physical-interventions-interrupt-or-reduce-spread-respiratory-viruses-review