Polyax design features a round shape of the head that works like a ball joint between the rim and nipple ensuring a better spoke/nipple line. Aluminum: 7075-T6 aluminum, special coating on thread and nipple surface to further reduce corrosion and reduce friction between spoke/nipple and nipple/rim. Brass: black or nickel coatedItem Specifications: Length: 12mm, Color: Silver, Material: Brass, Package: 100/Count, Gauge: 14g,