I got a raze on my ul pm6. I can't say enough good things about it.
It's almost twice as smooth as my cp sling, has magnetic return, and has sped up my bps by at least 5 with my left hand and even more with my right.
I'd be willing to bet it fits the dm4 just fine. I've only heard about it not fitting the pmr ul not anything else. You should drop an email to critical just to make sure though