I bought a set of used m4's and put them on my rig last night. The rear one was a pain to mount but i found out it was because my wheel was sitting to far forward in the horizontal drop out. No biggie. I gave it a little test run around outside and can already tell the modulation is 127865876435 times better than the hayes i was running. Now we'll see how they do on the race saturday. So far i likes em!