19-25 mm, are recommended for tuned scooters, as they increase both the 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 power increase with substantial RPM increases primarily in the upper RPM range. Very suitable for top speed. The PHVA 17.5 carburetor (order no. 7.432.728/9) is also suitable for tuning all PHVA 10-12-14 models! Not street legal! Item Type: Carburetor, complete. Features: Racing carburetor, not street legal. Type: PHBG