Beach RC says.... 

These will keep your brake pads disengaged while on throttle.  They are compatible with all NB48 and NT48 models and all brake linkages and configurations.

Vehicle Compatibility

• TKR5368B - Brake Pad Return springs (revised, x-stiff, all NB/NT48, 4pcs) is not included with any kit.
• This can be used with the NB48, NB48 2.0, NB48.3, NB48.4, NT48 and NT48.3 vehicles and should be a direct replacement for the stock part or used as a new feature. Please use the instruction manual for the kit(s) listed to verify compatibility and no additional items are necessary before purchasing.