This mask fits perfectly. I ordered a medium after using the measurement guide. It is exceptionally close fitting to my face, is very soft and comfortable to wear all day. My last mask had a filter pocket and I would have to put in fresh filters each day. Not needed here, you simply wash in cold water at the end of each day and leave to air dry naturally so it's ready for you in the morning. Quite a heafty price tag but hopefully worth it. For that price I would have liked it to come with its own bag for when you need to take it off. I don't like stuffing it into my pocket or bag and often don't know where the best place to put it is when out and about. But this is an issue with any mask you need to take off momentarily when out. I do feel confident and have far less anxiety wearing this quality mask, knowing that it fits properly and protects.