What is good about such reputable brands such as K&N and DNA is the information they list with regards to testing.
137.1 cfm @1.5 inH20
Filtration results also listed.
New DNA High Performance filter P-H2S11-01 for the Honda CBR 250 2011 | DNA Filters Ltd.
Honda | DNA Filters Ltd.
The filtering efficiency is extremely high at 98-99% filtering efficiency, with 4 layers of DNAŽ Cotton.
The flow of this New DNA Fcd filter is high, +29,50% more than the HONDA stock paper filter!
DNA Fcd air filter flow: 140,10 CFM (Cubic feet per minute) @1,5”H2O corrected @ 25degrees Celsius
Honda stock paper filter: 108,80 CFM (Cubic feet per minute) @1,5”H2O corrected @ 25degrees Celsius
Decent reviews on Amazon.
One of the suppliers in India had a batch that didn't include the frame in the box.
K&N sent them out to owners FoC.
With my slightly modified exhaust I will probably disconnect the battery for 10 mins and reset the ECU, at next weekend's 72k km service.