Features: Made of high quality zinc alloy, durable and rustproof. Unique external thread makes it insert hole easily and save effort. External thread ensures strong resistance against pull out. Flanged head prevents splitting of the surfaces and driving the insert too deeply. Provide a strong permanent thread for wood and wood based sheet materials. Specifications: Model: M8 Shape: Inner Hexagon Quantity: 20pcs Color: As pictures show Material: Zinc Alloy Length: 30mm/1.18in, 25mm/0.98in, 20mm/0.79in, 18mm/0.71in, 15mm/0.59in, 13mm/0.51in(Optional) Hex Width: 8mm/0.31in Package included: 20 x Hex Drive Head Nut 1Made of high quality zinc alloy, durable and rustproof. 2Unique external thread makes it insert hole easily and save effort. 3External thread ensures strong resistance against pull out. 4Flanged head prevents splitting of the surfaces and driving the insert too deeply. 5Provide a strong permanent thread for wood and wood based sheet materials.