Rotor took its road winning technology and finally released ovalized mountain bike rings, as well as single , double , and triple specific REX mountain bike cranksets this past fall. The QX2 is designed as the outer chainring for a 2 ring mountain bike drivetrain. Ovalized chainrings are essentially designed to maximize the efficiency of your pedal stroke by prolonging the power zone and minimizing dead spots. They are machined with a subtle oval shape and, with multiple mounting holes, can be clocked to maximize the effects for your biomechanics, pedaling style, and bike geometry. The QX2 features an ovality of 10%, which helps you accelerate better, experience smoother torque, and grip better off road. Additionally, the alternating thick and thin tooth profile keeps your chain from dropping even in the roughest conditions. This eliminates the need for a chain guide. The Rotor QX2 Outer Chainring comes in sizes: 104 38t, 104 40t, 110 36t, 110 38t, 110 39t, 110 40t, 120 38t, and 120 40t. Each ring comes in the color Black.