Specification:
- Displacement(c.c. / cu.in.): 14.96 c.c. / .913 cu.in. 
- Bore(mm / in.): 28.0 mm / 1.102 in.
- Stroke(mm / in.): 24.3 mm / 0.957 in.
- Practical R.P.M.(R.P.M.): 2,000 ~ 16,000 rpm  
- Output(BHP/RPM): 2.75 BHP / 15,000 RPM 
- Weight(g/oz): 562.2 g / 19.83 oz

The PRO engine series feature aerospace-technology ball bearings for supporting the crankshaft at high RPM while the Schnuerle-boost combustion porting delivers greater power and fuel economy. The Pro Series engines are equipped with twin ball bearings, twin needles and ABN-type piston and cylinder for years of trouble-free performance.

All Pro Series engines deliver exceptional power-to-weight ratio and value, making them fantastic 2-stroke powerplants for model airplanes.

The latest Pro-91 is a ringed-type engine equipped with a massive forged aluminum connecting rod and dual bushings. Its unique "squared" cylinder head design allows for cooler runs. Note that the pro-91 requires a muffler sold separately, either conventional type (No. 9225N) or Rare Bear custom-made muffler (No. 9791).

1.   Side exhaust
2.   Hypereutectic machined Al-Si ringed piston
3.   High strength connecting rod with bushings pre-installed
4.   XC2 (extreme composite coating) cylinder liner with special criss-cross pattern etched
5.   One-piece crankcase with squared-off shape cooling fins
6.   Dual ball bearing-supported crankshaft
7.   Vertical fins heat sink head for optimum air cooling
8.   2 Needle valves carburetor
9.   Swept-back needle valve for added safety adjustment
10. State-of-the art CNC machined components
11. Redline R2 glow plug included