![K&N luchtfilter Honda VTX1800C 2002-2008](http://tovami.com/cdn/shop/products/HA-1802_{width}x.jpg?v=1581017166)
This filter serves to replace the original filter. The great advantage is that the K&N filter does not need to be replaced with a new filter during maintenance. Instead, you can wash the filter and re-oil it.
The filter element is a cotton cloth soaked with a special oil. The cotton fibers absorb the oil and thus the dirt literally sticks to it. As a result, more dirt is retained, which is better for preserving the engine. In addition, due to its construction, the filter allows more air to pass through, which in turn benefits power. Especially when the K&N filter gets dirty and thus clogs up, K&N still lets a lot of air through where other filters no longer do.
It does not make a substantial difference for air fuel when a stock exhaust is installed, but in combination with other modifications it is definitely recommended to have your motorcycle finetuned. If the predecessor is a low quality filter, then obviously it does make a difference to the tuning.
Sets with K&N cleaning kits and filter oil are also available at Tovami