This is a very reliable vertical foregrip with pretty much nothing bad to say about it. I have it as one of two lower mounts on my Echo-1 614, which had a hard time mounting it since the rails were just barely too wide, but the proper application of some force (remove the barrel from the gun before you do this or you might accidentally bend the barrel) and grease should help you get it on. Unfortunately, it's just as hard to get back off, so unless you intend on never taking it off of that rail again, you may need to file down either the rail or the grip or both, which I did.
It's much more comfortable to hold than the bottom of an RIS rail (such as on the 614 and G36C)
It looks exactly like the Vertical Grip used by the US Army and Marine Corps (and probably other nations' armed forces too)
It is built very well and certainly helps your aiming when not using a bipod or propping up on something.
It may be difficult to mount on Echo-1 guns (I only know about the 614, but other rifles may or may not have similar problems. A friend of mine who has a JG G36C was able to mount his vertical grip with no problem, but I am not sure if the rails on both guns were exactly the same size)
For what it is, $20 seems a bit pricey, but every other vertical foregrip is at least that much unless you get one as a free gift or something.
If you're having a hard time storing your 614, you may want to instead get the folding grip so that you don't have to remove this one every time you're done with it. However, I've heard that the folding grip also has a hard time with the rails.
If you own anything with RIS rails and need something more comfortable, I'd certainly recommend this.
Rating: [4 of 5 Stars!]