The DeWalt Black & Decker 323711-02 SDS Spindle O-Ring Seal is a genuine OEM replacement sealing ring for selected rotary hammers and hammer drills. It fits within the SDS spindle assembly to provide an effective seal around the spindle, helping retain lubrication and protect the internal mechanism from leakage and contamination, and is suitable for replacing a worn, flattened, split or damaged original O-ring.