Made of 431 stainless steel with a buff satin finish, the RAC OS irons are based on the successful RAC (relative amplitude coefficient) wedge concept used on Tour. They feature four major innovative elements added, delivering better distance and the ultimate in forgiveness: a Tuned Performance Cartridge, an oversize design, a generous offset and two precision-milled pockets in the head cavity to channel impact vibration to strategic areas of the clubhead for the purpose of controlling feel, resulting in the best possible feel at impact.