Cleaning Rod
A one-piece coated rod that carries a jag or brush through the bore, ideally pushed breech to muzzle to protect the rifling and crown.
A cleaning rod is the shaft that drives a patch or brush down the length of the barrel. Serious precision shooters favor a one-piece rod with a smooth polymer or carbon coating and a rotating handle, since a coated shaft will not gouge the bore and the free-spinning handle lets the tip follow the rifling twist. Segmented multi-piece rods are convenient to carry but the joints can flex and scratch, so they are usually a field compromise rather than a bench tool.
How the rod is run matters as much as the rod itself. Pushing from the chamber end toward the muzzle keeps debris moving out the front and keeps the rod from rubbing the crown, the most accuracy-critical surface on the barrel. A bore-guide holds the rod centered on the way in, and the tip carries either a patch on a jag or a bore-brush depending on the step.