These are internally threaded and counterbored tubular rivets that can be anchored entirely from one side. With an open end, barrel-shaped flange and protruding boss that is internally threaded, this flat head rivet nut ensures a good performance of fastening. The boss sits within the components being fastened, the flange provides the bearing surface. Features: Made from zinc plated carbon steel which provides strength, corrosion protection and long service life. With open end, small flange, round hole, threaded inner wall and partial anti-skid surface, this flat head rivet nut has a good performance as fastener. Convenient to install, designed to form a bulge on the back side of the panel as a screw is tightened in its threads. There are seven different sizes from M3 to M12 that you can choose as needed for various purposes. Each set includes many pieces of rivet nuts so you don't have to go to hardware store searching rivet nuts for a while. Specifications: Material: Carbon steel Surface Finishing: Zinc plating Color: As pictures show Type: Flat head rivet nuts Size and Quantity(Optional): M3 100pcsM4 100pcs M5 100pcs M6 100pcs M8 20pcs M10 20pcs M12 20pcsPackage Included: 1set x Rivet Nuts