Q: What is the material of these knurled insert nuts? A: They are made of high quality brass, not easy to rust, and durable in use. Q: Do you have the M5 x 10mm x 7mm size? A: Yes, there are 20 PCS in the box. Q: What size screw does these take? A: They take M3 and up to 5mm can be threaded. Q: How many types of knurled insert nuts are these? A: There are 15 types in the plastic box.