07450 2-Speed Gear Box f. 1:6 Retrofitting is possible for all 1:5 and 1:6 FG Models. ( Not f. F1.) Adjustable shift point, high reliability, gearwheels can be changed in no time. During a competion we recommend to use the small gearwheels with 16-26 teeth in alloy or steel. The only difference between the gear 7450 and 7451 is the amount of teeth of the gear wheels and the corresponding alloy hub. If you use the gearwheels 7424/1 with 38 teeth you need the alloy hub A 47mm 7456/1.