4-inch diameter 90 Degree Rubber Elbow: Sy-Klone International
Pipe Fittings Direct. 4 inch Long Radius 90 degree Schedule 80 316 Stainless Steel Weld Elbow
L490-1818SA 4 inch 90 Degree 18 inch x 18 inch OD-OD
Amazon.com: NDS 4P02 PVC 90-Degree Elbow, X Hub solvent-weld connections, for Use with 4-Inch Sewer and Drain Pipes, White, 1 Count (Pack of 1) : Everything Else
Black, plastic "squeeze" 90 degree elbow for 4" ducting with mounting flange