The NEW TRIPLE roller option with a 1.25 diameter roller creates a very consistent smooth upshift and backshift with improved roller wear. This latest design creates a huge improvement in engine braking compared to our dual roller Tuner. All billet construction capable of using compression springs with different spring rate options.We have many helix angles see menu below. We can also provide custom helix angles to your desire for additional fees. We also offer the option of a encapsulated helix design that keeps the driven from unloading,opening and going into high gear during breaking and jumping which some racers require. Can be used along with the stock primary or the STM primary. Best results are aquired when running both the STM primary and STM Tuner together. When ordering use this guide to help you pick options Choose a model – Let us know what you have RZR pre 2010, RZR 2011-2013, or XP Number of shims – The amount of shims we install will determine your belt deflection or how tight the belt will be between your primary and driven clutch, keep in mind we are setting the deflection for a stock belt, for an RZR pre 2010 choose 1 shim, RZR 2011-2013 choose 3 shims, XP choose 2 shims Keep in mind the more shims you add the looser the belt less shims tighter belt, NOTE you want to have your belt as tight as possible without the bike creeping forward while in gear at idle. Choose a helix angle - The most popular helix is the 45deg. It’s a good all-around helix we found worked the best for the average to aggressive trail rider Choose a spring– The most popular spring is the PS13 gold this spring works well for most average to aggressive trail riders. If you have a turbo choose the kss12 blue spring. Comes with a belt removal tool and uses stock bolt for installation. KEEP IN MIND WE CAN ONLY GET YOU CLOSE WITH SET UP every ones riding style is different so it’s up to the customer to do the fine tuning!