Sram red etap 11 speed rear mechthe sram red etap rear derailleur will jump to the next cog in your cassette in an instant precisely and consistently and without a cable in sight srams own wireless technology provides a secure connection and the removable battery has a 1000km range so if you forget to top up your battery and it runs low miles from home simply swap it over with the front derailleurs battery to get back on the road with a full cassette range it also benefits from the same