5/16"-18 x 20mm Threaded Inserts for Wood, Hex Drive Wood Nut Inserts, Exceptional Threaded Insert Nuts for Furniture, Wooden Products and Models, 50 PCS. Features - The Threaded Nut Inserts are inserted into a pre-drilled hole, and the external protrusions bite into the wood in order to prevent the nut from either turning or pulling out; Easy to install and with good stability.
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