Forney 70487 Tube Brush, Nylon with Wire Loop Handle, 15-1/2

Does the metal core rust? Thanks.

Is the metal flexible and thin or rigid and thick? I need it to be flexible and bend. Need it to clean the little drain hole in the sink.

Is this large enough to clean a shower drain of soap scum and hair?

Description says: 15-1/2Long x 1-1/4x 5, tube brush loop end. Is the bristle diameter 1 1/4"? And will this fit through a 1/2" diameter hole?