f you decide to use a big-bore carb, you will have to replace the restricted manifold with an unrestricted one. Otherwise the large carb will be useless since its venturi size is actually reduced to the diameter of the restricted manifold. Our manifolds will fit any Dell'orto carb up to 21 mm. The derestricted manifold gives better acceleration and better top speed. Compatible with: - Aprilia: RS 50 -05 AM6_M, RS 50 -06 AM6_M, Tuono 50_M - Beta: RR 50_S - Yamaha: TZR 50_M