Slingshot 4D irons, from Nike, are mid-sized irons made of stainless steel with a variable sole: wider soles on long irons for higher launch, while short irons have thinner soles for better control. Slingshots also feature the Nike signature Slingback design, which places the sole weight toward the back of the club head on long irons and forward on short clubs. This, Nike claims, allows the player to achieve proper ball flight throughout the set. Shaft options include Speed Step SL steel and UST Slingshot graphite, available in standard flexes. Though this (and all) Nike clubs are no longer in production, Slingshot 4D irons are still widely available on the secondary golf market.