Designed to look like a better player’s muscleback blade in the address position, the Exotics C721 irons feature a moderately thin topline and modest offset. Still, they pack plenty of hidden technology to enhance distance and feel. The C721 irons are hollow to maximize the distance potential of the high-strength, 17-4 stainless steel cup face, which features Diamond Face 2.0. It wraps under the leading edge to improve performance on low-struck shots. But instead of having grooves only on the outer hitting surface and being smooth on the inner-facing side of the face, Tour Edge designed 92 diamond-shaped areas on the inner-facing portion of steel. These act like miniature trampolines, flexing and bending when the ball makes impact with the club to broaden the sweet spot and protect ball speed on off-center hits. Another advantage of the hollow-body design is it allowed Tour Edge to inject a lightweight, thermoplastic polyurethane in two areas. Referred to as Dual VibRCOR, the material soaks up excessive vibrations and improves sound and feel without impeding the face from flexing. Twelve grams of internal weight were added low in the heads to drop the center of gravity and pull it farther from the face. That should encourage a higher launch and a steeper descent into the greens for extra stopping power.