The compact size of this gearbox makes it ideal for installation into 135 scale tank models as well as some of the larger 148 scale tank models. The mini motor is highly efficient and produces very little noise, making it great for applications such as RC models for Educational Construction projects. Four gear ratios (71.4:1, 149.9:1, 314.9:1, 661.2:1) can be chosen for assembly. The gearbox case, gears, and crank are made from durable plastic material while the 3mm hex output shaft is made from metal. Furthermore, the gearbox case is transparent to enable viewing of internal mechanisms. Dimensions: (Width) 20mm, (Height) 24mm, (Length) 30mm.