i just went to install my FF III with the picatiny mount on my weaver style base and discovered the screw on the picatiny base is a little bigger than the slot on the base. I had to file the slot on my weaver base to get it to set flat. It looks like it will work fine but know I have another problem. Just be careful not to tighten the FF III with the 2 screws on to the base to much because the picatiny mount is aluminum and the screws strip easy. Know I have to order a new picatiny mount. My mistake. Hope this helps.