Outlets are inserted into a drilled or cut hole in the bottom of the guttering to attach the elbow to the guttering. 
White aluminum outlets are available in 2-3/8”, 2-3/4”, 2”x3” oval, 2”x3” rectangle, 3”x4” oval for 5”, 3”x4” oval for 6”, 3”x4” rectangle, 4”x5” rectangle, 3-3/8” round, 3” round, and 4” round for all sizes of guttering. 
Rectangle OutletRound OutletOval Outlet
Galvalume outlets are available only in 2”x3” oval, 3”x4” oval for 6”, 3” round, and 4” round. 
Galvanized Oval OutletGalvanized Rectangle Outlet
Copper outlets are available in all sizes but 3”x4” oval for 5”, or 3-3/8” round.
A modified outlet is used for the half-round guttering and is available in a 3” or 4” round in aluminum, galvalume, or copper.