This is a TT02 Rear Lower Arm set upgrade made with Aluminum. The lower arm set is specifically designed to have the minimum flexing area and lowest possible friction at the joints for smoother and more linear movements, which allows the rear dampers to react and absorb to bumps and weight shifting at a much better fashion. Yeah Racing highly recommend to use this item with their Rear Suspension Mount #TT02-011 for even better handling performance and rear grip.