it's a magpul RVG grip, one of the cheapest around...
I know we have a Canadian magpul dealer on this board but his price (39$+taxes+10$ shipping) makes absolutely no sense to me when I could be buying the very same item from Brownells (at regular, not dealer, pricing of 19,99+shipping) sell it cheaper than said dealer and STILL be able to make profit... So yeah, I got it from brownells.com
The rail is a special order I placed at Fabsport, it's a Yankee Hill part YHM-9465-6.
So all in all it was for me a 60$ upgrade including taxes and shipping, but I do not recommend doing it if you are not good with tools or new to the m14... The rail is installed with 3 machine screws and 3 matching nuts (not provided). I had to drill holes where I would have enough clearance to fit the nuts and clear the op-rod, I then cut the screws short enough to also clear the op-rod.