It looks like the F6 is the same as my VERY old F2 without the side pockets, the F3 is 12.5" left to right, so bigger than I want. The F8 is the fleece lined bag (my words), but would fit a 2 compartment insert nicely with room to spare on one end or the other. The F3 is nearly double the price of the others ($130), the F6 is $65, the F8 is $80 (plus $19 for insert). I can't deal with the zippered top of the other versions, I like to throw open the flap and have access. Who has which and is happy? Yes, I could just load up the old F2, but it is bigger than I'd like to carry these days, especially considering that this new kit is so small! PEN-related pics would be great!