Last week I bought a Harris BRM "S" bi-pod from Brownells. I wanted to get the pod-lock, but they were back ordered. http://www.brownells.com/.aspx/pid=1506/Product/KMW_POD_LOC
I needed some AR57 mags do I started browsing Midway USA's site. Found this.http://www.midwayusa.com/viewproduct/?productnumber=153528
Almost half the price of the pod-lock. The reviews were pretty good so I bought it. Bi-pod finally showed up today and I got it all installed. Very easy to install. It locks the rifle down hard. No way to do this with just the nut. I know alot of guys go with the pod-lock as its kinda like the standard, but if you want to save 10-15 bucks give this a shot!
Sorry bout the crappy picts. My camera is a pain in trying to focus up close. Here it is installed on my back up Pdog killer. R-15 VTR 22"