the 15 tooth sprocket changes your gear ratio, giving you more top speed(top end). In doing this, your rear tires will spin a lot less and hook up and go more taking off. The 700 raptors stock gearing spins away most of your power from 1st to 3rd gear. TRUST ME, this is one of ths first things i read on this forum, and IT WORKS!! Like someone before me said, "have you ever noticed how your raptor pulls like a freight train in 4th-5th? With the 15 tooth sprocket, it will pull like a freight train in EVERY GEAR". Your raptor pulls harder in 4th and 5th because none of your engine's power is wasted or "spun away". When you hit the gas in those gears (4th & 5th) , your tires hook up. think of it like limited slip transmissions on a car. You have two of the same cars lined up for a drag race. One has LSD(limited slip differential) and the other dosen't. Both mash the gas when the light turns green. One car spins out like crazy, while the other barely chirps his wheels, hooks up, and goes. BASICALLY the same concept... :thumbsup: