There are numerous brands of fly-tying bobbins on the market for sale. When purchasing a bobbin, it is difficult to find a good bobbin.  Most bobbins are open frame, you have a small frame that the threat is placed between two pressure points. The thread is threated up a tube either metal or ceramic.  The biggest problem with all the bobbins they don’t weigh very much. The solution is before you let your bobbin rest (meaning it’s not in your hand) is to add weight to the bobbin.   You can hook on a heavy dubbing spinner to the bobbin.  Or hook a fishing weight that you have cut out a small cut piece of the swivel, so you can hook the weight to the bobbin.  If you don’t add weight there is a good chance that your material on the hook will move. The second problem is adjusting threat tension. The threat tension should be very close to the breaking point.  Once you have secured your threat to the hook the bobbin should hang about 1” below the hook. Adjusting the tension can be problematic, depending on the brand.  Most bobbins can be adjusted with a pair of pliers; some have tension wheels which to tighten or loosen.  Is there one bobbin better than other? I have at least 15 bobbins and everyone of them have their unique problems. A plastic bobbin ends up in trash because they are worthless. I hope this was helpful.