The Orbit Bar Ends from PROTO are made 6061 aluminum, and fit over your crossbar. They are compatible with every single bar that adheres to the industry standard of 7/8" (0.875") crossbar thickness. This includes titanium, aluminum, and steel! A single m6 screw is used to secure the Orbit onto the bar.
Keep in mind that even if a bar adheres to the industry standard diameter, not all paint/plate/powder coat methods are the same thickness. This means you may have to tap the bar end onto the crossbar with a mallet before tightening the screw.