Rear - Front sprockets MJ rear sprocket for YCF Bigy 125 MX MJ Corse MJ.310 €28.19 High quality duraluminium (ergal) rear sprocket for YCF Bigy 125 MX with chain pitches 415 and 420 and with number of teeth from 30 to 46. Select the chain pitch and number of teeth you need by clicking below. Add to cart