These drivers were originally designed for those who were racing on asphalt. These are non-extrovert drivers are designed to drive off of the four row's of drive bumps found in between the track suspension rails. If your are purchasing for 1 snowmobile, you will need to order 2. These do not have antiratchet points and do not require trimming the rails. If you have a Polaris and your driveshaft is prior to the Aluminum Hex or Steel Splined shaft please refer to our Hex Shaft Drivers.