Hi David. The aluminum valve stems are Gr-3 parts for a bit lighter weight especially with heavier 10", 13" and 14" wide rear wheels. Some vendors (Hall, Larry Stock) have them on the shelf. They are not expensive but can be damaged by flying road debris. Safer to use slightly heavier chrome plated brass stems if you drive such roads. A few motorcycle shops also stock aluminum stems for lightness, and they're popular with rice-boy wheels in pretty anodized colors like red, blue and green. But with those you have to be careful on the sizes to fit in Campy's machined recess. And since the nut that retains the valve stem in a wheel is also aluminum, use anti-sieze or you'll be cutting the nuts away on the next tire change. Same goes with aluminum caps on aluminum stems.