This is the Thunder Tiger 90 Class High Performance Heli Muffler.
For OS and Thunder Tiger helicopter engines
Constructed of polished natural finish aluminum
90 Class Heli Muffler with Pressure Tap, Extension and Metal Gasket
Two 4x42mm Mounting Bolts
Two 4x12mm Mounting Bolts
Two 4mm Lock Washers
Requires:Fastening to engine