See: O.S. Engines

O.S. Engines have introduced the new Max-21XR-B Ver.Ⅲ nitro engine for 1/8th Buggy and GT cars. The power plant features a reduced piston weight improving throttle response while the connecting rod is the same used with the Speed engines in order to improve durability. The newly designed crankshaft also improves throttle response thanks to a new counter shape and timing. Always with a mind to offer more performance, the newly designed inner head features a redesigned the shape of the combustion chamber, improving response from low to medium speed range and achieve stable power characteristics in high speed range. The Max-21XR-B Ver.Ⅲ nitro engine comes with the double adjust J3-1 carburetor renowned for its ease of use and with two venturi inserts, a 6mm (orange) for the Off-road class and 7mm (yellow) for the GT class. The cooling head offers a new shape and a new design. Beside the single engine, O.S. also offers a combo package for Off-road use including the EFRA 2089 (T-2090SC) muffler and MB01-75 manifold and also a combo package for GT use including the EFRA 2042 (T-2060SC WN) muffler and MB01-70 manifold.