SMJ have introduced three new nitro engines, the 21XB2 Power and 21XB2 Eco are designed for 1/8 buggy and GT, while the R21 is made for 1/8 on-road. These engines have been produced by Masayuki Miura, the well-known mechanic of Atsushi Hara . The 21XB2 Power and 21XB2 Eco are based on the O.S. Speed 21XZ-B Spec II and the R21 is based on the O.S. Speed R2101.
The 21XB2 Power comes with 7mm venturi and it is particularly suitable for high speed tracks or GT, the 21XB2 Eco comes with a 6mm venturi is more suitable for low grip or wavy surfaces and the R21 comes with a 8.5mm venturi. The engines are pre-break in by Yurugix and the pre-break period is different according to the place where engine will be start up.