While the Ping G20 irons is made from steel

The Ping G20 irons features a lightweight Titanium insert forged directly into the back of the clubhead. The thicker Ti Muscle material behind impact ensures that the centre of gravity is located closer to the clubface, which allows better players the ability to work shots whilst still offering the forgiveness of the cavity-back design. The Ping G20 irons is an evolution of the succesful MP-58 model. With the Ti weight added to the Ping G20 irons, off-center strikes will benefit from even greater stability. The appearance of the Ping G20 irons is also improved by reducing the offset as a result of this improved stability. Thanks to the help of Mizuno's Tour Staff, the MP-59 iron now features a thinner top-line, a weightier sole and a new sole grind.
characteristics of the pure titanium placed behind the hitting area allows for the ideal amount of thickness behind the impact area to deliver consistent solid feel while simultaneously providing a dramatic increase in permeter weighting for enhanced playability. The stainless steel medallian presents elegant aesthetics.
While the Ping G20 irons is made from steel, 12 grams of titanium are forged into a pocket behind the face of each club.  Ping G20 irons says the titanium allows the clubs to maintain the ideal amount of thickness behind the impact area for solid feel while automatically redistributing the weight to the heel, toe and sole of the discount golf clubs. “The more you push the weight out to the perimeter and the thinner you make it in the middle, there’s a trade-off with feel,” says David Llewellyn, research and development manager for Ping G20 irons USA. “But by using a lower density material we can maintain thickness here and build in a little bit of forgiveness.”