SRAM XX1-A1 Bicycle chain

It might look normal from the outside, but the engineering inside this incredible chain design that makes possible a gear range previously found only in 2-chainring drivetrains. And it's also the biggest contributor to the Eagle drivetrain's ultra-smooth, precise, durable and quiet performance. The Eagle chain's links have a smooth radius, with no sharp edges or chamfers, which yield a significant reduction in noise, friction and wear on chainrings and cassette cogs. This design also allows for a flatter plate, which means more consistent chain riveting and greater overall strength.