The Nike Slingshot 4D irons add progressive change to four critical areas of performance to create irons that play how you need them to, when you need them to. Features: Slingback: Design positioned weight strategically (low and back in long irons; higher and forward in short irons) in each club to achieve the desired ball flight Variable Sole Width: Sole width narrows progressively throughout the set long irons are wider for higher launch; short irons are thinner to provide greater control