Kyosho BRG012O 8x16x4mm Open Bearing 2pcs

A pair of 8 x 16 x 4mm open ball bearings from Kyosho's universal bearing range.

Open means unshielded on both faces, and that is a deliberate choice rather than a cheaper option. An open bearing spins with less drag than a shielded one because there is no seal rubbing, and it can be flushed and re-oiled easily. That makes it the right choice for sealed positions inside a gearbox or differential, where the housing already keeps dirt out and what you want is minimum friction.

What it is not right for is any position exposed to dirt. Without a shield, off-road grit reaches the races within a run or two, and once inside it grinds them, drags on whatever the bearing supports, and eventually seizes. If you are replacing a bearing in an exposed hub position, you want the shielded equivalent instead.

Note that Kyosho makes a similar 8 x 16mm bearing in a 5mm width, so check the width as well as the bore before ordering. Two are supplied. Bearings are consumables: if one feels rough spun between your fingers, replace it rather than cleaning it.