JeremyBwrote a review of e*thirteen components Extended Range Cog on May 31, 2017
Familiarity: I've put it through the wringer
Make your old 2x10 into a 1x10. I made the switch without the extended range set up... it was not worth it. When I put it on the extended range gear it made a huge difference and my legs thanked me for it. Has no issues if adjusted correctly. Having a clutched rear derailleur also helps.