While the flashy clothes from Puma that Rickie Fowler wears when he competes on the PGA Tour get most of attention, some spectators no doubt are eyeing the irons he plays, too. These days, they are Cobra Amp Cell Pros. Company engineers say they developed the line with Fowler when he came to the club maker in 2012. At first, they made him prototype sets, and then with his feedback they developed what now is a consumer line under the Amp Cell Pro name. Forged of carbon steel, these blade-shaped clubs are geared for the better golfer. Fowler plays the muscle-back version of the Amp Cell Pros the whole way through his bag. But what are being made available at retail are so-called “flow” sets, which are what Englishman Ian Poulter uses on Tour. In those sets, the long irons – from 3 to 6 – utilize a dual cavity design. That flows into a single cavity for those clubs in the midrange – Nos. 7 and 8. And when it gets to the short irons – 9 and PW – the Amp Cell Pros employ a full muscle-back design, which technicians say deftly blends forgiveness, tour trajectory and workability.