This TKI CNC - TOM KOBZA INC- Billet offset 4 wheel axle kit (Now anodized black only) will allow SKI-DOO oem 180mm or 200mm wheels to be changed to 8" or 9". This reduces rotating friction by allowing the track to bend less as it rotates around the rear skid wheel. These are machined for 25mm bearings and the wheels must be ordered separately. ALl of our wheels have 25mm bearings included. These are a great addition to the 2015 Ski-doo's Freeride 137 and B/C for riders who run trail more than powder and gives a little extra security to make it home as the 2 wheel axles have ruined many a trip. These axles come with rail inserts for Ski-doo Xp, XM, XR, & REV GEN4. They also include rail adapers for Polaris , Arctic Cat, and Yamaha. All of our axles are hard anodized black for durability and cost $10 more than raw aluminum . Order 8" or 9"wheels separately.