This is an optional Tekno RC 3.0mm Rear Sway Bar. This sway bar is compatible with the ET48 and NT48 1/8 scale trucks, and is two steps stiffer than the sway bar included in the kit. Available Rear Sway Bars TKR5490: 2.3mm TKR5491: 2.4mm TKR5492: 2.5mm TKR5493: 2.6mm (stock) TKR5494: 2.8mm TKR5495: 3.0mm