This is a common question we get here at FMF Racing. You cannot add a spark arrestor screen to any existing 2-stroke silencer. The reason for this is because all of our 2-Stroke silencers that have spark arrestors, are built into the actual core as a "Turbine Dampening System" that is welded to the core and is U.S. Forestry Approved. The three silencers we offer with spark arrestors are the Turbinecore's, Q Series and the Q-Stealth's.