The threaded nuts are made of high quality zinc alloy, durable and anti-rust. The 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 Wood Based Sheet Materials. Specifications:Model: M4Quantity: 50pcsColor: as pictures showLength: 0.8cm/0.31inHex Width: 0.4cm/0.16in Weight: approx. 44gPackage Included:50 x Hexagon Nut Note:Please allow 1-3mm error due to manual measurement. Thank you for your understanding.