The 3M 501 Retainer. Plastic retainer used to attach either the 5N11 or 5P71 prefilters to 6000 series cartridge. KEY FEATURES : *Approved 3M system component. *Designed to hold 3M Particulate Filter 5N11 and 5P71/07197 ( AAD ) ( sold separately ). *Component works with 3M Respirator 5000 series, 3M cartridges 6000 series and 3M filter adapter 603. *Colour : Translucent white. *Measures 4" high x 8.5" long x 4.5" wide. Sold : 100 each per case. Part Number : 501