1 Replacement 3M™ Adflo™ pre-filter (part number 836010).

Features: 

Regular replacement of the Adflo™ pre-filter extends the life of the particle filter, saving money while also increasing the Adflo battery run-time
Inspect your pre-filter regularly for any damage, clogging or breakthrough
Do not attempt to clean the pre-filter
Replace once to twice a week for constant use 
For use with the Adflo system and 3M™ Speedglas™ welding helmet or 3M™ Versaflo M-Series face shield
If you also require a particulate filter, see part number 837010.