421688-7 supersedes older part numbers: 213854-8
Original Makita seal ring — part no. 421688-7 — a molded rubber sealing ring listed by Makita as "O RING 97" (Q'ty: 1) for the gear/gearbox area.
This genuine Makita sealing ring measures as the O‑ring 97 nominal size and is used to restore the gearbox/oil/dust seal on rotary hammer models such as HR3520.
If the old seal is cracked, flattened or missing, replacing it with this original Makita part will help stop oil leaks and keep dust out of the internal bearings and gearing; it’s the standard sealing ring called out on Makita service drawings.
Note: listed in Makita parts diagrams as a single sealing ring for the model gear housing — part number 421688-7.
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