Rear - Front sprockets MJ rear sprocket for Rotobox Model 1 MJ Corse MJ.729 €59.27 High quality duraluminium (ergal) rear sprocket for Rotobox Model 1 with chain pitch 520, 525 and 530 with number of teeth from 34 to 60. Select the chain pitch and number of teeth you need by clicking below. Add to cart