Machined from high-end aluminum, Promax 4-bolt 104 BCD chainrings are designed to handle the torque and stress of modern BMX racing and are fully capable in other single speed applications.CNC Machined from high grade 6061-T6 series aluminum for high strength while providing weight savings. Designed to be used with most cranksets and spiders that utilize a 4-bolt 104 BCD chainring. Item Specifications: Color, Black, Ring Position/Type, Single, Tooth Count, 41, Round or Oval, Round, Drivetrain Speeds, Single Speed 3/32", Chainring BCD, 104, Material, Aluminum, Defined Color, Black,.