Never seen the point of these. If you have a spare front der. lying around then you could just use that, as it will do the same thing. If you want good chain retention, then run a chainguide with at least a lower pulley to increase chain tension. I have used the Lopes SL which is pretty minimalistic, light, but excellent. This is a good option if you don't need a bash, which I assume you don't as the xcx won't work with bash either.