The MGN25083 is a 1-pole C60H miniature circuit breaker from the Multi9 range, rated 4 A with a D-curve. That D-curve means the magnetic trip is set at 12 x In (plus or minus 20 %), so it holds through the inrush of motor or transformer loads without nuisance tripping — the kind of thing you'd reach for on a pump or a small compressor feed.
That's a single modular width, so it fits a standard distribution board without stealing space from adjacent poles.
