Metal Extrusions Introduction
Below are some useful catalogs from different companies that can be used to select a metal extrusion.
80/20 - Online Catalog Page
Most popular company for aluminum extrusions. Preview their catalog with many different designs. The main website also has good resources to learn more about extrusions and contact the manufacturer for specialized sizing.
Granger - Online Catalog Page
Good selection of a variety of extrusions from a list of brands.
McMaster Carr - Online Catalog Page
An organized list of extrusions and their different types. It is easy to find the right one for your purposes.