Avon Protection GPCF50 CBRN Filter Black Pack of 4. The Avon GPCF50 Filter has a unique conformal shape providing a low profile close fit with the mask. When combined with an appropriate chemical protective mask the GPCF50 filter canister protects the face eyes and gastro-intestinal tract of the wearer against chemical and biological agents in aerosol liquid and vapour form. Package Contents: Avon Protection GPCF50 CBRN Filter Avon Protection 72601-70-20: GPCF50 CBRN Filter Black Pack of