The 9-0858-01 is an Air Filter that simply covers the intake barb on 9-1056-01 APG Ozone Module so that bugs, dust and debris don't get lodged into your ozone system, causing failure.
Most of the time, you can re-use the one(s) on your old APG Module(s). But, if you lost it, it got dirty, or you like to follow a routine maintenance pattern, change the Air Filter each time you change the APG Ozone Module (every 3-5 years).