Malleable Iron Pipe Fitting, 1-1/4 x 1/2 Inch Bell Reducer

That's exactly right. The larger opening connects to 1-1/4 inch pipe and the smaller end steps down to 1/2 inch. Both ends are threaded to American Briggs Standard, so as long as your pipe threads match that standard, you'll get a solid, leak-resistant connection on both sides.

For reducing between those two pipe sizes, that is exactly what a 1-1/4 x 1/2 bell reducer is meant to do. It has American Briggs Standard pipe threads and the openings are chamfered so the threaded connection starts easier.