To begin with, very fast shipping from TonZof.com. I placed my order on Saturday night and it was delivered to my door on Wednesday. It looks like you can buy it from different sellers, much like on Amazon, and the same quad rail is $4 cheaper from OpticsPlanet.com, but the only place it was available when I ordered was TonZof.com. As a bonus, free shipping, so I'm more than ok paying $4 more to have it delivered in a few days rather than weeks.
Now for the rail itself. First of all, it is not a 2 piece quad rail like it says in the description, it's a 3 piece. The top side is one solid piece and the bottom is made up of two pieces. One piece covers from the delta ring to the sling attachment, and the other from the bayonet lug flush to the end of the rail. With an extra pair of hands, the old hand guard came off fairly easily, even without the use of a delta ring wrench, and I installed this quad rail by myself.
True, there are no instructions, but installation was easy, and it can only be installed one way. Placed the butt of the rifle on a hard, flat surface, pulled down on the delta ring and popped the top side of the rail in place. Did the same with the bottom and then used the provided allen wrench to bolt the top and bottom halves together. The third piece attaches directly to the top part of the rail with 4 more allen screws...use the numbers on the rail pieces as a guide, and there's even a notch on the inside of the "floating" piece to accommodate the bayonet lug.
This quad rail even came with rail covers. I tried (not very hard) to put one on, just to see what it would look like, but gave up because I had already planned to buy some Magpul rail covers for it.
So far I am completely happy with it, even though I haven't attached anything to the rails and haven't had the opportunity to go shooting yet either, and wouldn't have a problem ordering it again.