The Allergy particle filter twin pack contains 2 spare filters.
This filter is able to trap Particulate Matter less than one micron in size and more than capable of the removal of PM2.5 Particulate Matter typically found in most city environments.
It can be used with any Respro® mask (with the exception of the Metro Mask) provided that it is the same size filter as the mask size ie; large filter – large mask.
For Instruction on how to replace a filter in a mask, watch the video here
Medium filters can also be used in a small mask.