This sprocket carrier is lightweight yet durable. They shaved off alot of weight by drilling holes throughout the aluminum hub area but has a thick spoke area for durability. It comes in 30mm and 50mm axle sizes. The 30mm is keyed for 6mm and 8mm so it will work with any metric chassis brand. The 50mm is keyed for the standard 8mm size. Made out of aluminum and anodized in 3 popular colors.