Shaft Model:REAX. The M2 irons also incorporate a geocoustic engineering design, which combines a specific shape and internal sound ribs to enhance both sound and feel at impact. One of the key features of the M2 irons is the “Speed Pocket” technology, which is a slot in the sole of the club that enhances face flexibility, resulting in faster ball speeds and more distance, especially on low-face strikes.
eBay