The O-Ring (OEM Part No. 0663210937) is a replacement sealing component used in the return accumulator assembly of Epiroc / Atlas Copco rock drills and drilling equipment. It is compatible with selected Boomer, Simba and FlexiROC models, including Boomer 282, Boomer L2D, Boomer M2C/M2D, Boomer S1D, Boomer T1D, Simba M7C, Simba S7D and FlexiROC T35. The 0663210937 O-Ring helps maintain pressure and fluid sealing within the accumulator assembly, reducing leakage and supporting stable hydraulic and rock drill operation. It is suitable for routine maintenance and replacement when the existing O-ring becomes worn, hardened, damaged or loses sealing performance.