The TR-6710N is a High Efficiency (HE) particulate filter for use with TR-600 Series PAPRs. The filter attaches directly to the motor/blower. 3M recommends the use of the TR-6700FC filter cover to help protect the filter from physcial damage. The TR-6700FC filter cover is also used to hold the TR-6600 prefilter or TR-662 spark arrestor in place.