This product is a set of vintage rare blue ball studs designed for the HPI RS4 Nitro 1, 2, Super, and Racer models. These ball studs are compatible with nitro and glow fuel and are suitable for 1:10 scale cars, trucks, and motorcycles. They are made by HPI, a Japanese brand, and are specifically designed for the RS4 Nitro model. The ball studs are used as suspension and steering parts and are a great addition to any collector's or hobbyist's RC model vehicle parts and accessories collection.