The diameter of the ends is meaningless. What does the fly end do after the end? How long is it that diameter? How long is the fat portion? How long is it before it's back to the diameter of the end? They should have told you something about the line when you bought it. What did that say? Did they tell you who makes it? Actually we can tell a lot by the answer of just the last two. Look for that information, and if you did not get it with it, tell us what set you got and who made it.
Here is something I got from a site explaining some of this for you.
1. Tip: a short 6-12 inch level section where you attach your leader. This section's role is to protect the line's taper. Since many anglers cut off a small part of fly line when they change leaders, the level tip allows these changes without shortening the front taper and altering the way the line casts.
2. Front Taper: this is the section of the line that determines how delicately or powerfully the fly is delivered. Typically, 4-8 feet long, it decreases in diameter from the Belly section to the Tip. This graduation of the line's mass (weight) determines its ability to transfer you casting energy.
3. Belly: because it is the widest diameter and longest length, this section is where most of the weight of a line is located and, consequently, where your casting energy is carried.
4. Rear Taper: decreasing in diameter from the thicker belly section to the much smaller diameter running line section, the rear taper creates the transition so important to casting smoothness.
5. Head: this term is used to describe the combination of front taper, belly and rear taper
6. Running Line: this section exists primarily to make distance casting easier.
Since a Double Taper (DT) line is essentially a long belly with tapers at both ends, there is no running line by definition. This large diameter belly line does not shoot through the rod guides easily. A smaller diameter, lighter weight line creates less friction. The running line portion of Weight Forward (WF) and Shooting Taper (ST) configuration fills this role. The Head is extended through the tip of the rod. The rod is loaded with the weight of the Head. Further extension of the fly line is accomplished by stripping line from the reel and then 'shooting' it through the guides.