Genuine DeWalt piston O‑ring — part no. 487287-00 — designed as the rubber seal that sits on the demolition‑hammer piston assembly. It restores the piston seal that maintains impact pressure and prevents internal air/oil leaks in DeWalt demolition hammers.

Fits many DeWalt/Black & Decker demolition‑hammer models, for example D25900K, D25940K, D25941K, D25901K, D25902K, D25899K and several D2573x/D2589x series tools — check your model parts diagram for exact fit.

This O‑ring is the replacement seal that pairs with the piston assembly (reference piston 582112-00 in DeWalt parts diagrams) and is sold as a single replacement seal. Installing a new 487287-00 O‑ring fixes common symptoms like loss of impact force or internal leakage caused by a cracked, flattened or hardened seal.

Compact, simple to install during piston servicing — keep one on hand to get your hammer back to full performance.