BMW M42 , M43 , M44 reinforcement girdle for NA engine aluminium AAMANN , 5 mm girdle plate aerospace aluminium, crmo spacers, 12.9 bolts, washers

Main bearing  girdle provides stiffening to your engine block. Since high forces act on the entire engine, especially in tuned engines, the use of girdle plates is advisable. They prevent the crankshaft from bending too much and withstand even high torques.