Genuine DeWalt part 578387-00 — a small plated metal spacer washer used in the cylinder/driver assembly of DeWalt rotary-hammer and hammer-drill tools. It protects the tube and mating surfaces from wear and provides precise spacing in the gearbox/impact assembly. Listed dimensions in DeWalt parts diagrams are approximately 28.4 mm outer diameter and 2 mm thickness (check your diagram for exact placement).

This washer is referenced on parts diagrams for a number of DeWalt models — for example: D25133K, D25134K, D25223K, DW557, DW25104K (rotary hammer/drill ) If your tool is one of these models and the washer in the cylinder/driver area is missing or worn, this original DeWalt 578387-00 is the direct replacement shown in the factory diagrams.

Supplied as the single metal washer shown in the parts breakdown — a simple, durable replacement to restore correct spacing and prevent premature wear in the hammer/rotary mechanism.