Callaway Apex 21 Iron SetCallaway Apex 21 Iron Set Introducing the NEW Apex 21 Irons. This is an extraordinary level of forged performance and craftsmanship never seen before. Its the first forged iron designed with Artificial Intelligence for faster ball speeds, and thats just the beginning. Callaway's world class R&D team has improved spin consistency using A. I., increased forgiveness from their massive Tungsten Energy Core, and enhanced the shaping for even better turf