Installed on a DPMS LR-308 20" Heavy Barrell Rifle:
Troy Industries MRF-308 Quad Rail:
http://troyind.com/MRFRails.html
Took the DPMS Railed Gas Block off the rifle and used this Sampson Low Profile Extended (to cover the A2 front sight post holes in the barrell) Gas Block:
http://www.samson-mfg.com/ar-15_html/product/LP-GB.html
I must say the install was a bit of pain in the ass. I had problems getting the Gas Block Roll Pin all the way through the Sampson Gas Block.
The Troy rail comes with it's own Barrell nut for DPMS rifles and requires you to file or dremel a part of the nut to allow clearence for the gas tube.
And I had to purchase the DPMS Free Float wrench to get the stock DPMS barrell nut off the rifle.
All in all it took awhle to gather everything together to do the install but it's done and the rifle shoots great and I think looks good.