STX Proton Power II Unstrung Head - Men's The original Proton Power head has been an industry leader since its beginning. Building on that success, the Proton Power II Unstrung Head now integrates STX's C-Channel technology for strength and stability. It evenly distributes stress across the rail so there's no pressure point that can lead to breaking or warping your head. Even with the added stability, this head doesn't lose its ball feel or snap. Includes additional stringing options so you can customize your performance.