Ping ISI irons. Ping's aim with these irons was to combine the accuracy of the Zing 2 model with the shot-making capability of the popular Eye 2. Ping's engineers achieved this goal through extreme perimeter weighting and a patented cavity design that has an ellipse and five vibration-absorbing fingers 'starburst' design. A more rounded shape, a cleaner top line, and alignment markings on the face give the golfer confidence over the ball. The result is that Ping ISIs feel solid, offer the playability that golfers need to control their shots, and are forgiving on mishits. There were two designs - this model - and the Ping ISI-K. With a thinner top-line and wider sole, this version is aimed at those looking for the advantages of a cavity back design with a more traditional feel. First launched in 1996 - Ping ISIs are so popular you can still buy them new from Ping.