Billet Head Kit - High Altitude - Matryx 9R - Polaris Increase cooling capacity for lower running temps which helps maintain peak power, High altitude kit gains 8-9 horsepower in the mid-range and 7-8 peak, Works in the 6000 - 9000 foot altitude range, Tune is required for the R9., 91 pump gas is required., BPR9ES NGK spark plug is by Bikeman Performance.