This is the "Race" filter, ie a filter that is the same shape as the standard filter, but the filter material has been constructed in such a way that there is increased air passage compared to other filter systems, but of course still maintains the filter effect.
 The BMC “Race” filter was designed for those who are not satisfied with the normal performance of the motorcycle, but rather modify the engine and the control unit in order to achieve more power afterwards. The “Race” filter can be recognized by a yellow stripe.