Made of piano wire material, full of elasticity;The net weight is only 4G, it is lightweight and compact, and will not bring you any extra weight. On the contrary, it will give you a comfortable feeling of use;1 piece per pack; (Note: The pocket knife in the picture is for reference only, not included in the pakcage. We do not sell pocket knives. )This spring fits for Microtech Combat Troodon series;Not applicable to other models!