The HiKOKI name has been around since 2018, when Hitachi Koki split from Hitachi and rebranded the power tools division. In practical terms for spares, very little changed. The same factories continued building most of the same tools, brush dimensions stayed identical across the rename, and a part that fitted a Hitachi-branded tool from 2017 almost always fits the HiKOKI version of 2019.
This matters because both names still turn up. Older trade kit is overwhelmingly badged “Hitachi”, newer kit on the same shelf is badged “HiKOKI”, and the model numbers carry across with minor adjustments. A C9U2 and a C9U3 circular saw use the same brushes; a DH26PB hammer uses the same brushes as the equivalent HiKOKI version. The full range is at Hitachi and HiKOKI carbon brushes.
Which brushes wear first follows the usual pattern: the brushed C-series circular saws, the DH SDS hammers, the G-series grinders. The brushes themselves are typical small-tool dimensions — 6mm by 9mm by 12mm is a common Hitachi size, with the lead either spaded or screw-down depending on the era. As with every brand, the original brush with the code stamped on the side is the cleanest possible reference; the rating-plate model number is the next-best fallback.
If the tool has been through more than one pair of brushes already, it is worth checking the armature for scoring. A brush that has been run too short will have worn a groove in the commutator, and a third pair of brushes won't last as long as the first. The brand-specific notes apply equally here — see the wider notes on carbon brushes for power tools for the symptom list.
For drill and screwdriver bits, blades, and other consumables, the cutting tools and drill and screwdriver bits ranges cover the rest of the kit list. The tool parts hub is the cleaner starting point if you want to search by part type than by brand.