The O-Ring (OEM Part No. 0663211346) is a replacement sealing component used in Epiroc / Atlas Copco DHR 6H Rotation Unit, COP 1638 and COP 2560 applications. It is installed within rotating and hydraulic assemblies to provide reliable sealing between mating components, helping prevent lubricant or hydraulic fluid leakage and reduce the entry of contaminants. The O-ring supports stable operation of associated internal components under demanding drilling and mining conditions. The 0663211346 O-Ring is suitable for routine maintenance, overhaul and seal replacement when the original component becomes worn, hardened, cracked or damaged. Public spare-parts documentation identifies this part as an O-Ring used in the DHR 6H rotation-unit assembly.