This is the Bisson Pitts Muffler for the .61 GMS engine.

FEATURES: Aluminum construction
Designed for engine installed right side up
Pressure fitting for fuel tank pressurization
Dual tube exhaust outlets
Bolt-through design

INCLUDES: One Bisson Pitts Muffler for the .61 GMS engine

REQUIRES: GMS .61 or Tower Hobbies .61 engine

SPECS: Length: 3-3/4" (95mm)
Width: 2" (51mm)
Height: 3-1/4" (82mm)
Exhaust Outlet Diameter: 0.29" (7.5mm)

COMMENTS: This Pitts muffler also works on the Tower Hobbies .61.
Although it fits the Tower and GMS .75 engines, the chamber size
is a little small for achieving maximum power.