Those are commonly sold in the MX community. I can't see how an RS would benifit though since it has an open air box. These are basically used in a portion of the airbox that has filtered air. They allow extra air in addition to what goes by the regular filter.
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james
Its not how fast you go...Its how you go fast.
MC21 Rothmans
RS250
RC31
CRF250X
748R
Porsche (many)
http://members.rennlist.com/j911brick/rennlist3_002.htm