It seems alot of people use this filter. I have a Redcat MPX90U. What part filter number do I need for it?

 

You would have to measure the carb flange and go direct to the K&N site and look under uni filters. You can scroll down till you find a filter with the same flange size then just pick one that will fit in the space that the filter occupies. There are hundreds of filters for just about anything. Make sure you get the outwears to go with it.

 

We have a Kazuma (Redcat) 90, and the carb inlet size is 1 1/4".