✈High Quality Steel: These hollow door anchors are made of High Quality Steel which offers some of the highest strength and grip, making it last longer than other hardware on the market today. They won't distort or deform soft plastics or thin sheet metals. ✈Excellent Finishing: Zinc plated, corrosion resistant, long service life ✈Easy to Install: A set of tool will give you a easy installation manually or electrically ✈Multi-Material Applications: Will not distort or deform soft plastics or thin sheet metal. ✈Quality Assured: DANA FRED molly jack nut has undergone testing to ensure a trouble-free installation Product Description1.Jack nuts are blind fasteners designed for assembly line use in thin, soft, or brittle materials. When tightened, the body collapses to form legs which grip the inside of the mounting surface, leaving a permanent, reusable threaded insert. From the Manufacturer2.The Jack Nut threaded insert is an economical blind fastener designed for assembly-line use in thin, soft or brittle materials. When tightened, the body collapses to form legs which grip the inside of the mounting surface, leaving a permanent, reusable threaded insert.size:Blue Zinc jacknutsM4*16-----20pcsM4*20-----10pcsM5*18-----5pcsM6*20-----5pcsM8*21-----2pcsBlack Zinc jacknutsM4*16-----20pcsM4*20-----10pcsM5*18-----5pcsM6*20-----5pcsM8*21-----2pcsNote:1, Warning: small parts, keep away from children and kids.2, If you have any questions, please feel free to contact us at any time.