19-25 mm, are recommended for tuned scooters, as they increase both performance and durability of the engines. They are mounted on original intake manifolds and original air filters (exception: Peugeot scooters, only racing air filters fit). Main jets may still need to be adjusted on some vehicles. - 19 mm = improved acceleration and torque - recommended for stop-and-go operation - 21 mm = significant performance increase with considerable RPM increases primarily in the upper RPM range. Very suitable for top speed. Carburettor PHVA 17.5 (order no. 7.432.728/9) is also suitable for tuning all PHVA 10-12-14 models! Not street legal! Item Article Version Complete Carburettor Features Racing Carburettor, not street legal Type PHBL