Original DeWalt O‑ring 580990-00 — direct-fit seal for DeWalt rotary hammers and SDS hammer drills. This small but critical rubber O‑ring is the factory DeWalt replacement used in the hammer/seal assembly to restore proper sealing and prevent oil/air leaks.

Typical listings give the size as approximately 16.4 × 9.7 × 4 mm (outer × inner × thickness) so you can verify fit if you’re measuring the old ring.

Fits a range of DeWalt hammer/drill models (examples include D25101, D25103, D25111, D25113, D25123, several D25124/D25134 variants and related D25304K / D25405K rotary hammers) — a compact, affordable part to replace a worn or damaged seal and get your tool back to working order.

Easy to install during normal disassembly of the hammer head or piston area — keep a spare on hand when servicing older DeWalt SDS/rotary hammers.