This is a set of threaded "rivet nuts" made of 304 stainless steel. The set includes 6 different sizes: M3, M4, M5, M6, M8 and M10. They are made of durable corrosion-resistant steel, resistant to high temperatures. The rivets have a flat head and an internal thread for screwing in bolts. Packed in a sturdy transparent box for storage and transportation. Such a set is often used in furniture making, car repair, household appliances, shipbuilding and industrial construction. But you can use them at your discretion wherever the situation requires it. Moreover, the manufacturer gives a lifetime warranty on the quality of this product. All in all, this repair kit is great for many everyday tasks.