Check the option parts that European Champion, EOS Champion and member of team XRAY Hupo Honigl from Austria has been using at his XRAY XB2'21. Hupo explains also the benefit of each part, for which track conditions they should be used and what performance improvement you will experience
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Differential Bevel & Pin & Satellite Gears #335030 Bevel & Gears #335080 Pin
>>> Because we use 2 gears in the diff most of the time, I definitely want to have the steel internals as they are a lot stronger and more consistent.
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#325003 Ball Adjust. Diff - LCG - Set
>>> Even when I do not always run a ball diff, I definitely want to have it ready in my box. I put it when the traction is low or the astro track is wet.
Rear Adjustable Drive Axle LB & Alu shim 10x12x2mm #325341 Axle #325390 Alu Shim
>>> The rear adjustable axle is a perfect option to fine tune the setup of my car.
Gamma Light Bodies for 1/10 2WD Off-Road Buggy #329713 Gamma 2C #329711 Gamma 2D
>>> The Gamma 2C and 2D light bodies are a great and simple setup option. Both work great on different style of tracks. A light body is also a must have on high bite tracks.