Metric thread,corrosion-resistant environmental protection.threaded inserts for wood.More Usage and Install: pre-drill a proper hole, screw-in with Screws Threaded Inserts. Fastener Connector Hex Socket Drive Threaded Insert Nuts For Wood Furniture Assortment.Applications: These furniture screws are suitable for furniture hardwood/ solid wood, for furniture combinations.Features of insert nut: These threaded inserts are inserted into a pre-drilled hole by screwing in, in that case the external protrusions bite into the wood, preventing the nut from either turning or pulling out.Material:Zinc alloycolour:Photo ColorPackage Contents:40 * Hex socket (M4*8)40 * Hex socket (M4*10)30 * Hex socket (M5*10)15 * Hex socket (M6*10)20 * Hex socket (M6*15)20 * Hex socket (M8*20)Only the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.