The Sting is free on Prime. Must have been 40 years since I watched it last. Think I'll watch it tonight. As I recall, it was quite good.
PS Many of the free movies on Prime state that they are free with ads. That's only the case if you watch them on PC. When viewed on a smart TV plug in device they are free and commercial free. At least that's the case when watched on my AppleTV. I assume it would be true on an Amazon Fire TV plug in, too.
