The PRO series helicopter ring-type engines are equipped with dual ball-bearings, Schnuerle porting, one ring-type piston / cylinder assembly and two-needles automatic mixture control carburetor. The PRO-Heli series are manufactured by automated computer-controlled machinery, resulting in a product that looks and performs better. The PRO-90H provides the smooth hovering and on-demand power and acceleration required by FAI pilots as well "hot dog" and "3-D" aerobatic fliers. Precision air bleed carburetor makes adjustments simple, and efficient mufflers keep things quiet at the field.

The Pro-50H and Pro-39H are two of Thunder Tiger's best selling engines because of their excellent performance and great value. The Pro-50H delivers smooth power for sport and 3D fliers. The new carburetor design provides incredibly reliable low idle rpm. The engine can turn at ticking rpm for extended time without flooding like many other engines. Compared to other 50 class engine, the Pro-50H is the most efficient in specific fuel burn, it is not unusual to obtain 10 to 20 percent longer flight time than competing 50 class helicopter engines. The Pro-50H also features very low vibration. This is a perfect motor for any of the Raptor 50 model. The Pro-50H works best in helicopters with gear ratios ranging from 8.5:1 to 9.1:1, and this engine develops peak horsepower at 14,000 to 17,000 rpm

The PRO series helicopter ring-type engines are equipped with dual ball-bearings, Schnuerle porting, one ring-type piston / cylinder assembly and two-needles automatic mixture control carburetor. Thunder Tiger’s .39 helicopter engines provide the smooth power for your demand. Displacement at .394 cubic inches is the largest displacement engine available in the popular 30-size helicopter class, and directly fit in all popular machines. Precision air bleed carburetor makes adjustments simple, and efficient mufflers keep things quiet at the field.