Hello,
I was wondering if anybody could post some experiences with DPMS Four Rail FF Tube?

I'm considering that vs. the FIRSH because it is only about $25 more for the standard length version, and my wife has me strapped into a budget for my "hobbies".

Thanks all!

I've got the carbine-length version on my M4. Had I to do it over again (and I will, eventually), I'd go with the Oly FIRSH.

The DPMS features Pic rails bolted to a vented FF tube. On the top rail, I had to remove two of the attaching hex screws b/c they interfered with the gas tube. Rail is still plenty secure, though. The top rail is also marginally higher than the flat-top rail (not a problem with the way I've got the gun set up). Construction quality is good and at the time, it was one of the only offerings on the low end of the market.

The rails on the FIRSH are integral to the FF tube, line up with the flat-top rail, and will not interfere with the gas tube. Installation looks to be a bit simpler, and the unit is cheaper than the DPMS ($99 vs $139 for the carbine version).