This is a must have on the 800R motor! We picked up 7-9 horsepower through the midrange and up to 5 peak horsepower. This new potent motor responded very well to the billet head kit without running big compression. We completely changed the interior dome shape, squish band area, and compression ratio for unbelievable gains on pump gas. Simply bolt it on and go, no jetting changes are neccessary. Available for both low and high elevations.