1.Made of carbon steel nickel-plated.2.M4 Thread.3.Suitable for standard 20mmx20mm aluminum profile extrusion slot.4.Easy to be roll into T slot of aluminum profile.5.Could be used together with T screw/hex screw Specification:Product Name: Roll Ball Elastic NutsMain Color: Silver ToneMaterial: Carbon SteelFinish: Nickel PlatedModel: 20s-M4Length: Aprrox.13mm / 0.51"Width: Aprrox.8mm / 0.31"Thickness: Aprrox.5mm / 0.2"Package Content: 20 x Roll Ball Elastic Nuts