Shimano 105 RD 5800 GS 11 Speed Rear Derailleur. It's not mere trickle down from Shimano's marquee Dura Ace and Ultegra groups but an out and out monsoon of awesome as 11 speed is available in the 105 level, exemplified by the Shimano 105 RD 5800 GS 11 speed Rear Derailleur. This medium cage rear derailleur compatible with cassette cogs up to 32t for mega low climbing gearing features a new spring mechanism and cable pitch to ensure that all important, perfect alignment. Its shifting action is lighter than ever, on the verge of being effortless, even when you need to change gears under maximum wattage. The time is now to make the leap to 11 speed and revel in smooth, precise gear changes all day long.