Imperial 8841 Rivet Nut Flange Knurl M4 X 0.7", 25/pack The knurls dig into the material, while the flange is created on the backside Used for adding a threaded nut to material that cannot be reached on the reversed side Works with oversize and irregular holes Applications include mounting side mirrors to doors, luggage racks, grab handles, battery trays and license plates to body Zinc yellow dichromate plating