Aluminum Spoke Arms are engineered and manufactured of Aluminum Alloy 6063 components and are heat-treated after weld to a T6 temper. Stainless Steel Mounting Hardware is included. Standard Spoke Arms are constructed of 2” NPS (2-3/8” O.D.) Schedule 40 Pipe. Center Hub is constructed of 3” NPS (3-1/2” O.D.) Schedule 40 Pipe. Custom designs including varying Pipe Arm diameters, Arm dimensions, and Center Hub sizes to accommodate varying Tenons are available.