`- Premium 2X Cannondale compatible rings are designed for the Hollowgram crank family including SI, SISL, SISL2, sold as a set only.\n- Rings are machined seperately, then connected together before directly mounting to the crank as one\n- Incredibly stiff and light with super fast shifting thanks to a patented shift ramp design\n- Oval rings help the rider spin smoother and generate more power and are optimized for each size seperately\n- Works with 2x chainring systems and does not require any modification to the front derailleur for use\n- Designed in UK, manufactured in Poland