The threaded nuts are made of high quality zinc alloy, durable and anti-rust. Unique external thread makes it easy to insert the hole and save effort. External thread Provides Strong Resistance Against Pull-Out Flanged Head Prevents Surfaces From Cracking And Drives Insert Too Deep. Provides A Strong Permanent Thread For Wood And Sheet Materials Based On wood. Specifications: Model: M4 Quantity: 50 Pieces Color: As Pictures Show Length: 0.8cm/0.31in Hex Width: 0.4cm/0.16in Weight: approx. 44 g Package Included: 50 x Hexagon Nut Note: Please allow 1-3mm error due to manual measurement. Thank you for your understanding.