M16-1.5×16 Castellated nut MB165 & MB200 Mini Bikes The M16-1.5×16 Castle Nut (short for “castellated nut”) is found on the jackshaft assembly on the Baja Mini Bike This castle nut attaches the large 20 tooth 420 chain sprocket to the jackshaft assembly The M16-1.5×16 Castle Nut (short for “castellated nut”) is found on the jackshaft assembly on the Baja Mini Bike. This castle nut attaches the large 20 tooth 420 chain sprocket to the jackshaft assembly. Compatible with both the MB165 MB200 versions. This M16 nut is also used on other Baja Motorsports products, including the RT50 SC50 50cc gas scooters. Thread Size: M16 Pitch: 1.5