My own personal experience with (non rubber/P100) respirators is that one with headbands (rather than ear loops) and a nose clip + nose foam is more likely to seal well.
To minimize the risk of getting counterfeits, it’s probably better to buy from a trusted retailer and prefer respirators for which the manufacturer offers some validation procedure (e.g. this one).
My own personal experience with (non rubber/P100) respirators is that one with headbands (rather than ear loops) and a nose clip + nose foam is more likely to seal well.
To minimize the risk of getting counterfeits, it’s probably better to buy from a trusted retailer and prefer respirators for which the manufacturer offers some validation procedure (e.g. this one).