The Roadlink extender can blow your road bike gears more into the mountain world. You don't have to change the derailleur along with the cassette. Simply remove the upper shifter arm from your existing derailleur and replace it with this identical twin, slightly longer. Designed for Shimano's GRX 810 (RX810), R7000 105, R8000 and RX800 Ultegra and R9100 Dura-Ace derailleurs. He can literally work miracles. Without sacrificing shifting precision, you get the option of fitting up to a 40-tooth cassette on your bike. Works great with both single and dual converter systems. Weight: 20g Made in USA