Allows for truing and tensioning of wheel using internal or external wrenches. 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 SL: 7075-T6 aluminum, special coating on thread and nipple surface to further reduce corrosion and reduce friction between spoke/nipple and nipple/rim. Secure Lock prevents nipples from loosening via a mechanical means instead of a thread locking compound or paste . Brass: nickel coated to ensure good corrosion resistanceItem Specifications: Length, 16mm, Color, Black, Material, Aluminum SL, Package, 100/Count, Gauge, 14g,.