Product Type: High quality hammer head drop in T slot nuts assortment kit Merterial: All of them are made of high hardness nickel plated carbon steel, with good rust resistance and better performance, durable for long time use ackage: This kit include 20 30 40 series with different size M3 M4 M5 M6 total 150pcs stored in a transparent plastic box, convenient for your storage and use Feature: They can be directly into the aluminum slot hole in any of the assembly post, back spring ball can be fixed its position which make installation very simple and reliable Application: T-Nuts suitable for 20/30/40 series aluminum profile, widely used for building industrial aluminum frame structures, 3D printers, CNC Routers, CNC laser cutters, robotics projects