Check the option parts that Bruno Coelho has been using at his XRAY XB2'21. Bruno 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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#325003 Ball Adjust. Diff - LCG - Set
>>> This ball diff is a must have for Astro tracks
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#325341 Rear Adjustable Drive Axle LB
>>> I use this to play with the position of the pin to find the best setting for the conditions I am in
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Alu Multi Adjustable Rear Upright & Hub Plate
#323355 Rear Upright
#323381 Hub Plate
>>> The alu multi adjustable rear upright and hub plate for it is a must have for carpet and astro as it improves rotation and handling.
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#326181 Stainless Steel Battery Weight 35g
>>> I use this weight under battery to lower the center weight
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#322572 Alu Steering Plate Rearward Linkage Mounting
>>> I use the alu steering plate because it gives me better feeling on the steering
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Composite C-Hubs & Steering Block- Graphite
#322210-G Right C-Hub
#322220-G Left C-Hub
#322250-G Steering Block
>>> These composite c-hubs together with steering block improve overall steering
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#322110-G Composite Suspension Arm Front Lower - Graphite
>>> This front suspension arm gives me more corner speed and less traction roll on carpet.
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Front wing and holder
#321190 - Graphite Holder
#323512 - Lexan Wing 0.75mm
>>> The front wing together with the holder improve overall steering
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#326183 Stainless Steel Weight 17g - Front-Middle
>>> I use this weight under speedo servo to lower the weight
