The Shim (OEM Part No. 3128311578) is a mechanical spare component compatible with Simba M4C, Simba M40S,Simba H1354, SIMBA H1254, underground drilling rigs. Manufactured from durable alloy steel, it is designed for the rock drill assembly rotation unit position. The shim is used for precise adjustment, spacing, and alignment between mechanical components, helping maintain correct assembly tolerances and stable operation of the rotation system. Its strong construction provides accurate fitting, reliable support, and long service life under demanding underground mining conditions. This OEM replacement shim helps maintain equipment accuracy, reduce component wear, and improve overall drilling system reliability.