These are my first ever pair of Oakleys.  I bought them primarily for running and cycling.  I had been wearing cheap supermarket sunglasses prior to these, and never had a pair last more than a month or two without breaking.  Fortunately, the Flak Jackets have performed flawlessly for me over a long Summer of pretty heavy abuse.  My number one requirement was that they needed to stay put on my face, without breaking due to snugness.  In that regard, the Flak Jackets have been perfect.  I have never once had an issue with them falling off or needing to be adjusted mid-run.  They are also showing no signs of stress or breakage whatsoever.  Additionally, the optics are night and day better compared to the cheapies I had been wearing before.  Everything is crystal clear, and water and sweat just kind of beads off the lenses.  These certainly aren't inexpensive, but they are easily worth the Amazon price I paid for them.  I would definitely buy them again.

As a side note, I had initially purchased the Half Jacket 2.0s, and they were way too snug for my wider face.  So if you have a wide face and can't decide, the Flak Jackets are probably a better bet over the Halfs.