OS GF40 Petrol W/F-6040 SilencerThe GF40 is the first ever OS four stroke petrol engine and is designed to offer the benefits of four stroke operation to a new size of model. That softer, scale sound can now be used in models designed for 33cc 2 stoke engines. In fact, the GF40 has the same mounting bolt configuration as the GT33 as well as the same distance from the rear of the mount to the propeller driver. Unlike full size 4 stroke engines (car and aircraft) the GF40 does not use