3Ì D7925 Ð2 R pre filter. Particulate filter of P2 protection level to be used with quad air flow 3Ì D8000 series Secure Click™ gas cartridges. This pre filter provides protection against solid and liquid aerosol particles. D701 retainer is used to clamp pre filters on to gas filters. Pack of 4 pre filters. Price per 1 pack.