Space for paper filter, fits snugly, stays in place.
Other masks slip off my nose or up from my chin.  Need constant adjustment.  This covers all, stays in place.  Ear straps are adjustable to right length for head size.  Inner pocket doubles thickness, and accommodates a paper filter in addition.  (Excellent paper filter can be cut from a Vacuum cleaner bag).  You can tell it is working as the sides gently move in and out with each breath.  Thus, air is not just escaping and entering around the sides, as some masks with openings there, but is passing through the filter.
Rating: 5 stars