griehle262077 wrote an answer about Oakley Flak Jacket XLJ Replacement Lenses on March 7, 2009
The Flak Jacket lens is ever so slightly larger than the Half Jacket lens, enough where they are not interchangeable. I have a pair of Half Jackets and they broke while I was changing lenses, so I checked at the store before buying the Flak Jackets to see if I could use the lenses that I have in the new frames. Sorry, they don't work. I really like the Flak Jacket though, so I got them anyway. They have really good coverage.