If you think that an open racing air filter is too loud and there is enough room in your helmet compartment you should think about using Dopplers new air boxes These systems have a connection size of 35 mm which may be reduced to 32 mm via the metal spacer included in the delivery and an interior diameter of 20 mm With its size of 21 cm length and 12 cm height it fits into nearly every modified helmet compartment Available in various colours