New Ultegra R8000 series is "pro-proven" as it is a direct trickle down from DURA-ACE groupset. With road bike components, the stress-free operation is one of the most important feature to lead all day riding comfort with braking and shifting. The Shimano Ultegra HG800 11-Speed HG-EV, 11-34 road cassette is designed to work specifically with GS cage rear derailleurs. This combination offers a wider range and lower climbing gears, perfect for mixed surface riding. The HG800 cassette Is compatible with both 10 and 11 speed freebodies.