This is OTA 188 Replacement Filtering Element Waterproof.
BMC Replacement Filtering Element for Oval Trumpet Airbox Kit - 188mm Length (Waterproof)
BMC air filters make use of cotton for the filters rather than paper which can guarantee you higher air flow because cotton minimizes the loss of air flow pressure. Dense paper filters can cause dirt and grime to build up with the filter. The design of the BMC filter with a special cotton that is soaked with low-viscosity oil can manage the accumulated dirt because the oil layering in effect suspends the contaminant away from the fibres and as a result the filter material is free for the next time it is needed.