Gutter outlets when fitted in the conventional way (from top side of gutter) are a major cause of rubbish build up and gutter rust, because a ‘ridge’ is created obstructing water flow out of the gutter. The Rain Harvesting 3″ Gutter Outlet fits from the underside of the gutter – no obstruction, so debris and fine particles wash out. Suits 3″ round downspouts.