GAUGE DESIGN MUSCLE BACK IRONGauge Design Muscle Back Iron(Japanese Made) Our new USGA conforming irons. 3 PW muscle back iron set. The lower center of gravity iron with larger sole promotes a strong ball flight with slight offset allows for increased ease of play for higher handicap players. This combination provides a very solid and unique feel with the workability of a true muscle back. The Japanese Made Gauge Muscle Back Iron is very much a players club but also is very