TaylorMade RSi1 4-PW, AW Iron Set with Graphite Shafts Face Slot Technology makes the TaylorMade RSi1 Iron their longest iron, even when you miss the sweet spot. With TaylorMades Advanced Face Design that features their thinnest face, a deep undercut, and Inverted Cone Technology, you get a club that promotes maximum face speed and advanced forgiveness. Advanced construction and multiple dampening systems improve sound and feel, while the new Reax 90 graphite shaft from True Temper helps to optimize ball flight for ultimate distance and performance New Face Slot Technology in the 3-8 Irons: Two slots located near the heel and toe of the club face that provide uniform flexion across the face Protecting ball speed and generating more consistent distance on off-center hits Improved Speed Pocket with ThruSlot Technology in the 3-7 iron: Provides ball speed protection on shots below the center of the face Increases launch angle and ball speed on all shots in.Weve taken everything weve learned about Speed Pocket Technology and have been able to apply it into the face. Face Slot Technology provides greater consistency across the face, giving players improved performance on mis-hits. And you can only find Face Slots in RSi. in. Tomo Bystedt Director - Product Creation Iron, Putter, Wedge