copied from another post:
Let's start with the similarities:
*Both filters use an oiled, cotton gauze media
*Both filters use polyurethane frames
*Both filters are cleanable and reusable with similar service intervals. Note that we would never recommend waiting for 50K miles unless you drive in a very clean, dust free area.
*Both filters are tested to ISO5011 standards. We use an outside test lab-in this case, Southwest Research Institute in Texas
The testing has shown that our filters have a 98%-99% cumulative fractional efficiency, which is the percentage of dust particulates that the filter traps. K&N also has a good rating.
Our SuperFlow Flow Bench testing shows us that the air flow between the Spectre filters and K&N filters is virtually the same.
When you increase the air available to the motor, you can pick up both performance and mileage (depending on driving habits). If you purchase a Spectre hpR filter and are dissatisfied with it, give us a call....we'll make it right!
-Dave
Spectre Performance