These MTX Hornet rear sprockets are CNC machined from case hardened chromoly steel. They are lightweight for a steel sprocket at only 26 grams (alloy sprockets are usually about 12 grams) and built to last. Steel sprockets easily out last alloy sprockets. The Hornet rear sprocket has a nickel finish which provides corrosion and wear resistance. These are one of the best steel sprocket available, they last and dont look like a bulldozer part.