Joes Adjustable RR Birdcage (double bearing) gives your team a whole new level of options to find the perfect balance point for maximum speed. Fine tune your adjustments to the smallest increment. Laser etched adjustment marks make it easy to record your settings. Championship proven 5½” center to center gives you the forward bite you need with maximum drive off the rear tires. Fits 1¾” axles. Additional insert required for most applications.