These are the third generation design of our wildly popular 2WDW ZX6R Velocity Stacks that we developed a few years ago while building several engines for club level and Moto America racers alike! We have updated the design to utilize OEM-style rubber, which makes installation MUCH simpler than previous designs AND allowed us to further reduce the cost of these velocity stacks through mass production with our friends over at TST Industries! Installation is now just a simple as removing and replacing the OEM velocity stacks. We were unhappy with the performance of the other velocity stacks on the market for these bikes. They either provided significant top end gains at the cost of equivalent midrange losses, OR they would provide decent mid range gains with virtually no top end performance improvements. Our velocity stacks are designed to offer the best of both worlds! With proper ECU mapping to match, you'll pick up 8-10hp at the very top of the RPM range with minimal midrange losses AND a much smoother power curve all the way to 15K RPMs.   As always, if you have any questions, don't hesitate to send us an email at support@2wheeldynoworks.com. We're always happy to help!