Capacitor Module X, Non Polarity, for XR10 Pro G2 (Modified & Stock Racing) For some racers, size and weight is a crucial component of their racing program. In that regard there are "smaller" lighter weight Stock style power cap modules that offer an improvement over the standard capacitors, without the added size and weight of the full size modified power cap modules. These can be used in the popular "stock" or "Spec" class racing. If size and weight are not a concern, the larger "Modified" power cap modules are the way to go. If you have size, fit, or weight topics that are of major concern, the "Stock" power cap modules are the way to go.