The fly line should have a label saying 'reel end' which is tied to the backing
Pros of the Peak Design Everyday Backpack Specifically good for drone people
One point to bear in mind here is that manufacturers often label reel models with sizes that relate to fly lines for single-handed rods, so a reel designed for a 10wt saltwater line will not take a 9/10 or 10/11 speycasting line and backing
After that, I did the research, reading reviews online from consumers and other outdoor journalists.
catfish,bass,trout,salmon,bluegill,stripers,walleyes,big crappie,etc
All while finding time to test the latest and greatest for Cycling Weekly