All of these options are for complete systems, including head pipe and muffler. The S option is for a Silencer only while the S/A is for a system with a Spark Arrestor.

The latest version of the Powercore 4 design incorporates a hi-flow core which mas more surface area to absorb more sound while flowing more exhaust. The silencer is constructed with an extruded aluminum canister is MIG/TIG welded and has space age internal packing. This system is lighter, stronger and provides more power than stock exhausts. The pipe is a stainless steel unit for strength and weight savings.

Powercore 4 S/A has a US Foresty approved, maintenance free, stainless steel spark arrestor screen to be sure you are safe and legal in the woods.