I've been using mine for about 3 months now and it works great. On my Avenger, I attach it with rubber bands. On my Prod the long metal clamp will go over the air tube and barrel shroud. I tried making a wood and metal adapter so I could put it on a little tripod but that did not work. The only drawback for me is it shifts my POI to have it on the shroud of the Prod - haven't tested that on the Avenger. So velocity and accuracy testing are two separate steps. The price is so low I don't see why any air rifle shooter shouldn't have one. You need a chronograph to tune your gun. I may still replace my old shooting chrony (that got shot one too many times testing inside with air rifles) so I can do accuracy and velocity testing in one step - outside when the weather cooperates. But I will still want this little one for inside testing or just for getting a quick reading without all the setup required for a caldwell or other more traditional chrony. While the FX has more features I can't see spending the price difference when this one works so well.