Meet Co-Founder Marty Jertson  The Stack System is the hottest speed training aid in golf.  Dr. Sasho Mackenzie, golf’s leading biomechanist, team up with Marty Jertson, PING VP of Fitting & Performance, to package an array of proven speed training protocols into TheStack App with a single training club that enables 30 precise mass combinations.  The StackApp acts as a personal speed trainer; customized programs that dynamically change based on performance, workout timers with optimized rest times, and hands-free data capture which feed relevant performance metrics, so you get the most out of your training.  There are over 10,000 golfers actively training with TheStack and over 4.5 million swings tracked which continuously feed A.I. training algorithms.  Matt Fitzpatrick after winning the US Open by overpowering the course, said "I'll be honest, it's worked wonders". Want 10% off?????????  Code: COOLCLUBS