We made ours from billet aluminum. Brake fluid is hygroscopic (absorbs water from the air) and soon rusts the can out.
We use the Wilwood caps because the ones from Moss dent if you look at them wrong. Also, they don't seal worth a dang and the brake fluid sloshes out and runs down the can eating the paint off the can (and anything else in its path). So, we went with billet aluminum to solve all those problems. Unfortunately, billet aluminum isn't cheap...but we sell a LOT of them--especially to the Shelby CSX4000 guys.
David
