The mask is pretty small
The mask is pretty small. I'm 5'-11" and 170 lbs, so not large or overweight, using the medium to large mask. It's difficult to get an air tight seal, and even when that is possible it's easily broken. My 3M respirator has no issues like that and also has a silicon face plate. Major difference there is more space between your face and the filter. Castle Grade should look at that design and see what can be improved in theirs. Average sized guys are probably going to have an issue with the fit. Might help if you have a small nose. Even smaller guys should probably get the medium to large size. I would buy an extra large version if it comes out due to the high build quality.