3M™ Secure Click™ Particulate Prefilters can be attached to 3M™ Secure Click™ Dual-flow Gas & Vapour Filters D8000 Series to provide particulate protection from certain solid and liquid particles when used with 3M™ Secure Click™ Reusable Respirators. Use the 3M™ Secure Click™ Filter Retainer D701 to attach two pre-filters to each filter.