Fly fishing reels today vary in size and complexity. They are made for everything from the average trout all the way up to sea run steelhead. The best reels are made from a solid block of aluminum like the Ross reel in this video. Lower cost fly reels are made from cast or stamped steel. I would not waste my money on one.
As you can guess, the drag systems designed for large steelhead can get really complex. To learn more about fly reel drag systems for steelhead click here.
Here is a short video from the Discovery Channel (How It’s Made) on how fly reels are made today.